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community dent oral epidemiol 2002 30 81­90 printed in denmark all rights reserved copyright c munksgaard 2002 issn 0301-5661 development of a conditionspecific quality of life measure for patients with dentofacial deformity ii validity and responsiveness testing cunningham sj garratt am hunt np development of a condition-specific quality of life measure for patients with dentofacial deformity ii validity and responsiveness testing community dent oral epidemiol 2002 30 81­90 c munksgaard 2002 abstract ­ the assessment of quality of life is becoming increasingly important in dentistry this may be measured using two groups of instruments generic and condition-specific objectives this paper describes the processes of validity and responsiveness testing of a condition-specific quality of life measure for patients who present with severe dentofacial deformity requesting orthognathic treatment the so-called orthognathic quality of life questionnaire the development of the instrument is described in a previous paper method the oqlq was tested for validity using a visual analogue scale and also the short-form 36 health survey questionnaire responsiveness was tested using longitudinal data obtained before during and after orthognathic treatment results and conclusions the oqlq shows good evidence of validity and responsiveness this together with previous evidence of good reliability suggests that the instrument may prove useful in both clinical trials and in quality assurance susan j cunningham1 andrew m garratt2 and nigel p hunt1 1 department of orthodontics eastman dental institute university college london london and 2unit of health-care epidemiology institute of health sciences university of oxford oxford uk key words dentofacial deformity health related quality of life orthognathic treatment quality of life susan j cunningham department of orthodontics eastman dental institute for oral health care sciences university college london ucl 256 gray s inn road london wc1x 8ld uk tel 44 20 7915 1000 ext 1317 e-mail s.cunningham/eastman.ucl.ac.uk submitted 6 april 2000 accepted 5 march 2001 the measurement of quality of life for purposes of health care evaluation is a rapidly expanding area with over 1000 new articles each year indexed under the term quality of life 1 patient-assessed measures of health outcome that include quality of life considerations are becoming increasingly important as researchers have realised that traditional outcome measures are of little relevance to the patient 2 the comprehensive evaluation of healthcare interventions requires outcome measures that are of importance to the patient as well as the clinician patientassessed health outcome measures are based on the assumption that in addition to relieving clinical symptoms and prolonging survival a primary objective of any intervention is the enhancement of quality of life and well-being 3 patient-assessed measures of health outcome are gaining increasing attention for purposes of healthcare evaluation monitoring of patient care and health policy and resource allocation 4 there are two broad forms of patient-assessed measures of health outcome generic instruments that provide a summary of overall health and specific instruments that focus on a particular disease or client group the strengths and weaknesses of the two approaches make them complimentary 5 6 generic instruments can take into account multiple conditions enabling them to measure wider effects such as the influence of co-morbidity on health their general nature makes them suitable for comparisons between different groups of patients and general or disease-free populations 81

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cunningham et al 7 8 generic instruments have greater potential to capture unforeseen effects and side-effects of an intervention which may go undetected by a specific instrument the narrow focus of specific instruments has the potential to make them more responsive or sensitive to clinically important changes in health resulting from health care interventions specific instruments can be selected that reflect the areas considered by patients or clinicians to be of greatest importance and can be specific to a particular disease population function condition or problem 6 9 10 the importance of quality of life in the field of dentistry has been acknowledged relatively recently although oral health was first considered in terms of quality of life during world war ii when the presence of six opposing teeth was utilised as an indicator of oral functioning/well-being and was used to assess suitability for service oral diseases seriously impair quality of life in a large number of individuals and they may affect various aspects of life including function appearance interpersonal relationships and even career opportunities 11 traditionally there has been a tendency to treat the oral cavity as an autonomous anatomical landmark located within the body and the oral cavity has been seen as separate from the body and the individual this approach is now being questioned and has given rise to new concepts in which oral conditions are linked to diseases in other body locations and to broader health and quality of life considerations 12 locker 12 also challenged the distinction often made between general and oral health and introduced the issue that our focus should be not on the oral cavity itself but on the individual and the way in which the oral condition affects health well-being and quality of life when oral health is compromised overall health and quality of life may be adversely affected 13 a number of quality of life measures now exist in the field of dentistry currently the best known of these measures is the oral health impact profile or ohip 14 15 which was designed for older patients to determine perceptions of the social impact of oral disorders this index has been widely used mainly on patients over 60 years of age other instruments include the social impacts of dental disease which was one of the first socio-dental indicators 16 the geriatric/general oral health assessment index 17 and the dental impact profile 18 all of these instruments were originally developed for use with an ageing population patients with severe dentofacial deformities may require a comprehensive orthodontic and surgical approach to their treatment orthognathic treatment and improved quality of life is one of the aims of this form of intervention the patients presenting for this form of treatment are normally young and fit which limits the relevance of the existing instruments this was the basis for the development of an instrument specifically targeted at this group of patients this instrument is known as the orthognathic quality of life questionnaire oqlq the development and reliability testing of the instrument have been described previously 19 the aim of this study was to test the validity and responsiveness of the instrument material and methods data collection ethical approval was obtained from the joint research and ethics committees of all units involved the evaluation of the instrument took place within an existing longitudinal study of orthognathic patients in three orthodontic/maxillofacial units in the south east of england sixty-five patients were recruited for this study and the oqlq was administered at three times first before any active treatment started t1 secondly following pre-surgical orthodontics/prior to surgery t2 and thirdly 6­8 weeks following removal of fixed orthodontic appliances t3 the questionnaire also included a 100 mm visual analogue scale vas which measured patients global self-ratings of appearance and function the short-form 36-item sf-36 health survey was included at t2 and t3 5­7 the mean duration between t2 and t1 was 17.1 months sd 5.4 months the mean duration between t3 and t2 was 7.7 months sd 1.8 months a total of 65 patients were recruited for the longitudinal study from whom 62 questionnaires were returned response rate 95 at t2 and used in validity testing of these respondents 39 were female 23 were male and the mean age was 21.92 years 95 ci 20.3­23.5 years data from the first 30 completed cases were used for the responsiveness testing of these individuals 17 were female and 13 were male there was a mean age of 23.2 years 95 ci 20.5­25.8 years outcome measures development of the instrument and the reliability testing are described in an earlier paper 19 the development of the instrument used standardised 82

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quality of life and dentofacial deformity procedures for item generation item reduction and testing these methods have been used previously in the development of a number of condition-specific instruments 20 21 the resulting orthognathic quality of life questionnaire oqlq consists of 22 statements marked on a four-point scale according to how much the issue covered by the statement bothers the respondent appendix 1 the 22 items contribute to four dimensions o social aspects of dentofacial deformity items 15­22 o facial aesthetics items 1 7 10 11 14 o oral function items 2­6 o awareness of dentofacial aesthetics items 8 9 12 13 oqlq dimensions are scored so that lower scores indicate better quality of life and higher scores signify poorer quality of life the 100 mm visual analogue scale vas was marked from 0 to 10 the respondents were asked to rate how they felt about their dental and facial appearance and oral function with 0 being no problem at all and 10 being the worst problem imaginable the sf-36 is the most widely used patient-assessed measure of health outcome and is often used alongside condition-specific instruments for purposes of assessing validity and responsiveness 5­7 the instrument consists of 36 items that contribute to several health scales including physical functioning social functioning role limitations vitality mental health pain and general health perceptions each scale is scored 0­100 where 0 is the worst possible and 100 the best possible health there is good evidence for the validity reliability and responsiveness of the sf-36 in different populations 4 6 22 23 the developers of the sf-36 have reduced the original eight-scale profile to two summary measures without substantial loss of information by reducing the number of statistical comparisons summary measures make clinical trial and other longitudinal data more interpretable the physical health component summary score phcs and the mental health component summary score mhcs have demonstrated reliability validity and responsiveness in both us and uk populations 24 25 lated to oqlq scores this included the eight scales of the sf-36 and a 100 mm vas which measured respondents own global ratings of their appearance and function juniper et al 26 suggested that correlations of 0.2­0.35 0.35­0.5 and greater than 0.5 are poor moderate and strong respectively and these values were adhered to in this study the sf-36 is a general measure of health with limited application in dentistry hence it is difficult to specify a priori expected levels of correlation however the following hypotheses were constructed based on a thorough knowledge of the literature and also the clinical judgement of several clinicians the oqlq primarily addresses mental rather than physical health therefore it was hypothesised that there would be moderate negative correlations between the domains of the oqlq and the sf-36 mhcs and that there would be poor correlations with the sf-36 phcs in addition the oqlq social aspects domain and dentofacial aesthetics domain were expected to have moderate negative correlations with the sf36 scales measuring aspects of mental health social functioning mental health role-emotional general health and vitality the oqlq oral function domain was expected to have fewer correlations with the sf-36 but in view of the number of patients who complain of difficulties eating and of embarrassment when eating in public a moderate negative correlation with the sf-36 scale of social functioning was proposed the oqlq awareness of dentofacial aesthetics domain was also expected to have fewer correlations as the items had a very narrow focus however a moderate negative correlation with the sf-36 mental health scale was anticipated the four domains of the oqlq were expected to have low levels of correlation 0.35 with the sf-36 scales of physical functioning rolephysical and bodily pain finally all four domains of the oqlq would have moderate positive correlations with the 100 mm visual analogue scale instrument scores were correlated using spearman correlation coefficients responsiveness testing if the oqlq is to be used in an evaluative context then it must be responsive to small but important changes in health the responsiveness of the oqlq was assessed by comparing scores before and after treatment responsiveness was tested using the first 30 completed cases with data at t1 t2 and t3 the validity testing in the absence of a gold standard measure of the impact of dentofacial deformity on patients quality of life validity was assessed through comparisons with measures that were expected to be re 83

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cunningham et al change in scores for the oqlq and the vas selfrating of appearance and function were calculated between t2/t1 and t3/t2 the change in sf-36 component scores was calculated at t3/t2 only the standardised response mean srm was used to assess the responsiveness of the oqlq the sf-36 and the vas self-rating of appearance and function the srm is equal to the mean change in score divided by the standard deviation of the change in score and allows meaningful comparisons between different instruments 23 srms of 0.2 0.5 and 0.8 represent small moderate and large clinical changes 23 24 at t3 a health transition question was included in which respondents were asked if their dental facial problems were much better/better/the same/worse or much worse than before treatment results tables 1­4 fig 1 table 1 shows the correlations between the scores for the four domains of the condition-specific measure oqlq the visual analogue scale and the sf-36 scales with the exception of four comparisons which showed no association between the scores all the correlations were in the direction hy pothesised all four oqlq domain scores showed a significant small to moderate level of correlation with the vas global self-rating the largest correlations were for the domains of social aspects and dentofacial aesthetics slightly larger levels of correlation were found with some of the sf-36 scales the domain of social aspects had statistically significant moderate correlations with the sf-36 mhcs ª0.50 and scales of mental health ª0.47 vitality ª0.40 and social functioning ª0.38 a smaller level of correlation was found with the scale of general health perception ª0.26 but this was still statistically significant the domain of dentofacial aesthetics showed significant correlations of a similar magnitude with the same sf-36 scales however this scale was found to have larger correlations with the scales of social functioning ª0.48 and general health perceptions ª0.40 but lower correlations with the scales of vitality ª0.34 and the mhcs ª0.43 the oral function domain showed only one significant correlation with any of the sf-36 scales or note that as quality of life improves the score for the oqlq decreases and for the sf-36 increases scoring is in opposite directions table 1 validity testing correlationsa of the condition-specific measure oqlq with the vas and sf-36 scales at t2 n62 oqlq scores domain 1 social aspects vas sf-36 components pf ­ physical functioning rp ­ role-physical bp ­ bodily pain gh ­ general health vt ­ vitality sf ­ social functioning re ­ role emotional mh ­ mental health sf-36 physical health component summary score phcs sf-36 mental health component summary score mhcs 0.45 ª0.10 ª0.08 ª0.07 ª0.26 ª0.40 ª0.38 ª0.22 ª0.47 0.16 ª0.50 domain 2 dentofacial aesthetics 0.44 ª0.09 ª0.14 ª0.18 ª0.40 ª0.34 ª0.48 ª0.22 ª0.46 ª0.13 ª0.43 domain 3 oral function 0.34 ª0.23 0.07 ª0.17 ª0.33 ª0.24 ª0.11 0.10 ª0.10 ª0.23 ª0.06 domain 4 awareness of dentofacial aesthetics 0.27 0.13 ª0.13 0.19 ª0.26 ª0.15 ª0.23 ª0.17 ª0.29 0.32 ª0.35 a spearman correlations p 0.05 p 0.01 scoring vas 0­10 with 0 being the best possible and 10 being the worst possible situation sf-36 0­100 with 0 being the worst possible and 100 being the best possible quality of life oqlq is scored such that higher scores represent lower quality of life and vice versa social aspects domain 0­32 dento-facial aesthetics domain 0­20 function domain 0­20 awareness of dento-facial aesthetics 0­16 84

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quality of life and dentofacial deformity table 2 validity testing comparison of hypothesised and actual findings for hypothesised moderate correlations of 0.35­0.5 n62 oqlq domain social aspects scale for comparison visual analogue scale sf-36 social functioning sf-36 mental health sf-36 role-emotional sf-36 general health sf-36 vitality sf-36 mental health component summary score mhcs visual analogue scale sf-36 social functioning sf-36 mental health sf-36 role-emotional sf-36 general health sf-36 vitality sf-36 mental health component summary score mhcs visual analogue scale sf-36 social functioning sf-36 mental health component summary score mhcs visual analogue scale sf-36 mental health sf-36 mental health component summary score mhcs actual correlation 0.45 ª0.38 ª0.47 ª0.22 ª0.26 ª0.40 ª0.50 0.44 ª0.48 ª0.46 ª0.22 ª0.40 ª0.34 ª0.43 0.34 ª0.11 ª0.06 0.27 ª0.29 ª0.35 hypothesis rejected no no no yes yes no no no no no yes no borderline no borderline yes yes yes yes no dentofacial aesthetics oral function awareness of dentofacial aesthetics a spearman correlations p 0.05 p 0.01 table 3 validity testing comparison of hypothesised and actual findings for hypothesised poor correlations of oqlq domain social aspects scale for comparison sf-36 physical functioning sf-36 role-physical sf-36 bodily pain sf-36 physical health component summary score phcs sf-36 physical functioning sf-36 role-physical sf-36 bodily pain sf-36 physical health component summary score phcs sf-36 physical functioning sf-36 role-physical sf-36 bodily pain sf-36 physical health component summary score phcs sf-36 physical functioning sf-36 role-physical sf-36 bodily pain sf-36 physical health component summary score phcs actual correlation ª0.10 ª0.08 ª0.07 0.16 ª0.09 ª0.14 ª0.18 ª0.13 ª0.23 0.07 ª0.17 ª0.23 0.13 ª0.13 0.19 0.32 0.35 n62 hypothesis rejected no no no no no no no no no no no no no no no borderline dentofacial aesthetics oral function awareness of dentofacial aesthetics a spearman correlations p 0.05 summary scales this was the correlation with general health perception ª0.33 the awareness of dentofacial aesthetic domain showed a statistically significant correlation with the mental health scale ª0.29 and with the sf-36 phcs and mhcs 0.32 and ­0.35 respectively tables 2 and 3 compare the hypotheses with the actual findings table 2 shows which of the hypothesised moderate correlations were supported 13 of the suggested hypotheses were proven although with two at borderline levels table 3 shows a comparison of hypothesised poor correlations with actu 85

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cunningham et al table 4 responsiveness testing data for changes in scores between t1­t2 and t2­t3 n30 instrument oqlq social aspects dentofacial aesthetics oral function awareness of aesthetics social aspects dentofacial aesthetics oral function awareness of aesthetics v as t2-t1 t3-t2 short-form 36 physical functioning role-physical bodily pain general health vitality social functioning role-emotional mental health t3-t2 t3-t2 t3-t2 t3-t2 t3-t2 t3-t2 t3-t2 t3-t2 6.15 2.03 5.86 2.02 95.00 92.50 85.90 71.50 62.17 82.93 80.00 69.23 12.93 20.92 18.23 16.65 19.81 23.54 29.88 21.22 5.86 2.02 1.47 1.13 96.00 90.83 83.57 71.50 65.50 82.03 74.27 72.80 6.21 26.65 22.55 19.57 23.17 25.54 37.91 20.16 ª0.29 2.29 ª4.39 2.01 1.00 11.92 ª1.67 30.75 ª2.33 25.70 0.00 17.55 3.33 24.08 ª0.90 29.52 ª5.73 45.79 3.57 23.63 0.13 2.18 0.08 0.05 0.09 0.00 0.14 0.03 0.13 0.15 time period between follow-ups t2-t1 t2-t1 t2-t1 t2-t1 t3-t2 t3-t2 t3-t2 t3-t2 mean score sd at baseline 15.07 13.27 8.23 7.20 15.30 14.40 10.03 7.80 10.39 5.92 5.51 5.40 9.99 4.65 5.13 4.22 mean score sd at follow-up 15.30 14.40 10.03 7.80 9.30 8.30 6.50 7.03 9.99 4.65 5.13 4.22 8.14 4.68 4.03 4.16 mean change sd 0.23 1.13 1.80 0.60 ª6.00 ª6.10 ª3.53 ª0.77 6.89 3.72 5.75 3.01 8.41 5.41 4.31 4.61 srm 0.03 0.30 0.31 0.20 0.71 1.13 0.82 0.17 t1prior to treatment t2after pre-surgical orthodontics/prior to surgery t3after removal of orthodontic appliances p 0.01 p 0.001 al findings in this case all hypotheses were supported by the data although with one at borderline level the remaining results represent the findings for responsiveness testing figure 1 shows the domain oqlq scores at all three time points and shows a significant reduction in the mean oqlq score following surgery for three of the four domains fig 1 responsiveness testing comparison of mean oqlq domain scores at all three times n30 p 0.01 p 0.001 scoring in all cases 0 is the best quality of life and increasing scores indicate poorer quality of life social aspects 0­32 dento-facial aesthetics 0­20 function 0­20 awareness of dentofacial aesthetics 0­16 table 4 compares mean scores at t1 t2 and t3 and also gives the srms for the oqlq sf-36 and the vas self-rating srms were considerably higher for the oqlq and vas than for the sf-36 in addition the srms for the t3­t2 time period were much greater than those for the t2­t1 period those in the t2­t1 period represent only a small clinical change while those in the t3­t2 period represent larger changes the highest srms were found for the vas 2.18 and the social aspects 0.71 dentofacial aesthetics 1.13 and oral function 0.82 domains of the oqlq for the t3­t2 period the value for the fourth domain awareness of dentofacial aesthetics was much smaller 0.17 although still greater than any of the srm values for the sf-36 components those values for the sf-36 during this period were very small in comparison the health transition question provided further evidence of responsiveness with the majority of respondents reporting positive outcomes 24 stated that they felt their dental/facial problems were much better than prior to treatment five said they were better and only one felt that the situation was worse 86

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quality of life and dentofacial deformity discussion the development of the oqlq followed a rigorous process of development and testing and the instrument has demonstrated good evidence of internal and test-retest reliability 19 however before the oqlq can be recommended for use in evaluation of orthognathic treatment it must also be assessed for the measurement properties of validity and responsiveness the oqlq has now undergone rigorous testing for validity and responsiveness validity testing validity was assessed through comparison with a vas and the widely used sf-36 health survey questionnaire when a number of correlations are undertaken there is always the possibility that some will be significant purely by chance however a priori hypotheses are necessary in these situations and the majority of hypotheses made were supported the correlations between the vas global self-rating and the four domains of the oqlq were all significant the social aspects and dentofacial aesthetics domains produced the greatest correlations ­ 0.45 and 0.44 respectively these components account for the largest variation in health 19 and larger correlations with the vas are therefore to be expected it is difficult to predict the relationship between a global question of aesthetics and function such as the vas and the broader based patient-assessed instrument however the constructs were sufficiently related to expect a moderate correlation and this was confirmed for the purposes of comparing the instrument to the sf-36 a number of hypotheses were generated which on the whole were confirmed by the data moderate levels of correlation were found between the oqlq social aspects and dentofacial aesthetics domains and the sf-36 scales of social functioning mental health vitality general health perception and the mhcs the correlation with the sf-36 scale of role-emotional was lower than hypothesised ª0.22 for both domains and was not significant however the correlation was much greater than for the remaining three sf-36 components relating to physical health which was expected there was a very low non-significant correlation between the oqlq oral function domain and the sf-36 scale of social functioning rª0.11 the lack of correlation may indicate that the hypothesis was incorrectly formulated as only one item i don t like eating in public out of five in this do main related to social aspects the significant correlation with general health ª0.33 may suggest that eating problems and functional difficulties lead to negative thoughts about general health it was hypothesised that a moderate level of correlation would be found between the awareness of dentofacial aesthetics and the sf-36 mental health scale a significant correlation was found although this was slightly lower than hypothesised ª0.29 the final hypothesis was confirmed with poor levels of correlation being found between the oqlq domains and the sf-36 scales with a primary physical component the only exception was a significant small level of correlation between awareness of dentofacial aesthetics and the sf-36 phcs of the 20 moderate correlations 0.35­0.5 hypothesised 13 were confirmed all but three of the 20 hypotheses gave significant correlations even if some were at a smaller level than predicted all of the 16 poor levels of correlation hypothesised were supported by this data with a few exceptions these results tables 2 and 3 related well to the specific hypotheses overall there was a tendency to significant moderate correlations between oqlq domains and sf-36 mental health scales and non-significant poor levels of correlation for the oqlq and sf-36 physical health scales similar findings were noted in a study by atchison et al 27 which used both the general oral health assessment index and the 14-item medical outcome survey stronger correlations existed for mental health components than for physical function these findings offer support for the validity of the condition-specific instrument the correlations between oqlq and the physical and mental health components of the sf-36 further supported the validity of the condition-specific instrument by showing stronger significant correlations between the oqlq and the sf-36 mental health component summary score this was anticipated as the instrument primarily addresses mental health these results provide good evidence for the construct validity of the oqlq in which the proposed underlying hypothetical constructs were largely supported by the data 28 responsiveness testing the responsiveness of the oqlq was assessed by following up 30 subjects over two time periods t1­t2 and t2­t3 sample size was in accordance 87

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cunningham et al with a number of previous studies including work by guyatt et al 29 who used 13 patients in one study and 28 in another the responsiveness of the instruments was quantified and compared using the srm none of the domains showed a significant change between t2 and t1 but the p-value which was closest to significance was found for the oral function domain p0.06 mean scores for the function domain were worse at t2 than at t1 this was probably due to the effects of the orthodontic appliances making eating biting etc more difficult this domain appears to be the most responsive to orthodontic intervention at this stage intervention had been limited to orthodontic treatment which produces less dramatic changes than the surgery itself it therefore appears that this stage of treatment did not influence quality of life to such an extent that significant changes were noted three of the four domains showed a significant improvement between t2 prior to surgery and t3 at the end of treatment social aspects dentofacial aesthetics and function this result was as expected primarily due to the surgery but removal of the orthodontic appliances may also have had an effect the fourth domain awareness of dentofacial aesthetics did not alter significantly between t2 and t3 this is the domain that appears to be least affected by the intervention and this is supported by the magnitude of change in the domain scores these finding suggest that respondents still tend to focus on their own and other s face/teeth following treatment and that this still bothers them to some extent however it is understandable for patients to be very much aware of aesthetics when they have just undergone a facial change it would be interesting to chart the progress of patients over time to see if respondents eventually show significant improvement in this domain or indeed any changes in the other domains when the changes for the oqlq domains are compared with those for the vas and sf-36 it can be seen that there was no significant change for the vas between t1 and t2 or for any of the sf-36 scales between t2 and t3 only the vas between t2 and t3 showed a significant change p 0.001 standardised response means srms are given in table 4 between t1 and t2 the oqlq domains of dentofacial aesthetics function and awareness of dentofacial aesthetics produced small srms 0.30 0.31 and 0.20 respectively compared to a much smaller srm for the vas self-rating of appearance and function 0.13 however it must be noted that the changes for the oqlq were indicative of a poorer level of health whereas the vas represented an improvement mean scores of 6.15 at t1 and 5.86 at t2 thus a short-term decrease in health during pre-surgical orthodontics was detected by the oqlq but not by the vas this suggests that the oqlq domains were responsive to the negative aspects of pre-surgical orthodontic treatment between t2 and t3 the vas global selfrating produced the largest srm and the oqlq domains of social aspects dentofacial aesthetics and function also produced large srms the oqlq therefore shows good responsiveness to changes due to intervention the sf-36 gave very small srms and was unresponsive to changes between t2 and t3 the use of a vas to measure global self-ratings of appearance and function is recommended for use alongside the oqlq in future studies however the multi-dimensionality of the vas is a limitation single item measures are less reliable and the ability of the vas to capture all patient concerns is borne out by the moderate levels of correlation with the oqlq domains the oqlq is based on individual patient experiences of the effects of dentofacial deformity on everyday life and hence has content validity from the perspective of the individuals undergoing treatment this makes the oqlq potentially responsive to changes that are important to the individual content validity is established where the items are representative of the area of interest and cover all relevant aspects and where the instrument makes sense to the respondent the results of the health transition question that was included at t3 lend further support to the responsiveness of the instrument with all but one respondent stating that their dental/facial problems were better or much better than at the start of treatment although the sample size was relatively small for the responsiveness testing it is comparable to previous studies in addition that significant differences were found in the oqlq scores after treatment and that acceptable validity was demonstrated supports the claim that the instrument has acceptable psychometric properties general this study and the previous paper 19 show that there is good evidence for validity reliability and responsiveness of the oqlq the oqlq was 88

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quality of life and dentofacial deformity found to be acceptable to respondents and this is supported by the high completion rates it is also brief making it suitable for use alongside other instruments for example generic measures or psychological assessments the instrument is likely to be of clinical relevance in situations such as clinical trials for example comparing the effects of single jaw and bimaxillary surgery and in quality assurance it has long been suggested that dentofacial deformity affects quality of life and that orthognathic treatment leads to improved quality of life this study goes some way to providing support for these suggestions the study also serves to highlight the limitations of generic measures of health status such as the sf-36 which performed poorly acknowledgements the authors wish to thank all the patients who contributed to this study and all the consultants who allowed access to their patients also to the two anonymous referees for their very useful comments appendix 1 please read the following statements carefully in order to find out how important each of the statements is to you please circle 1 2 3 4 or n/a where 1 4 23 n/a means it bothers you a little means it bothers you a lot lie between these statements means the statement does not apply to you or does not bother you at all 2 3 4 bothers you a lot 1 2 3 4 n/a 1 2 3 4 n/a 1 2 3 4 n/a 1 2 3 4 n/a 9 i spend a lot of time studying my teeth in the mirror 10 i dislike having my photograph taken 11 i dislike being seen on video 12 i often stare at other people s teeth 13 i often stare at other people s faces 14 i am self-conscious about my facial appearance 15 i try to cover my mouth when i meet people for the first time 16 i worry about meeting people for the first time 17 i worry that people will make hurtful comments about my appearance 18 i lack confidence when i am out socially 19 i do not like smiling when i meet people 20 i sometimes get depressed about my appearance 21 i sometimes think that people are staring at me 22 comments about my appearance really upset me even when i know people are only joking 1 2 3 4 n/a 1 2 3 4 n/a 1 2 3 4 n/a 1 2 3 4 n/a 1 2 3 4 n/a 1 2 3 4 n/a 1 2 3 4 n/a 1 2 3 4 n/a 1 2 3 4 n/a 1 2 3 4 n/a 1 2 3 4 n/a 1 2 3 4 n/a 1 2 3 4 n/a 1 2 3 4 n/a references 1 muldoon mf barger sd flory jd manuck sb what are quality of life measurements measuring br med j 1998 316:542­5 2 dijkers m measuring quality of life methodological issues am j med rehabil 1999;78:286­300 3 berzon ra in staquet mj hays rd fayers pm editors quality of life assessment in clinical trials ­ methods and practice oxford oxford university press 1998 ch 1 4 jenkinson c wright l coulter a quality of life measurement in health care a review of measures and population norms for the uk sf-36 oxford university of oxford press 1993 5 ware je measuring patients views the optimum outcome measure br med j 1993;306:1429­30 6 garratt am ruta da abdalla mi russell it responsiveness of the sf-36 and a condition-specific measure of health for patients with varicose veins quality life res 1996;5:1­12 7 ware je sherbourne cd the mos 36-item short-form health survey sf-36 i conceptual framework and item selection med care 1992;30:473­83 8 euroqol group euroqol ­ a new facility for the measurement of health-related quality of life health policy 1990;16:199­208 9 juniper ef guyatt gh development and testing of a 1 bothers you a little 1 i am self-conscious about the appearance of my teeth 2 i have problems biting 3 i have problems chewing 4 there are some foods i avoid eating because the way my teeth meet makes it difficult 5 i don t like eating in public places 6 i get pains in my face or jaw 7 i don t like seeing a side view of my face profile 8 i spend a lot of time studying my face in the mirror 1 2 3 4 n/a 1 2 3 4 n/a 1 2 3 4 n/a 1 2 3 4 n/a 89

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