In their comparison of the CIS-R and CIDI lay diagnostic interviews for anxiety and depressive disorders with reference to the clinician- administered SCAN in 105 attendees at one primary-care practice Jordanova and colleagues

To the Editor : In their comparison of the CIS-R and CIDI lay diagnostic interviews for anxiety and depressive disorders with reference to the clinicianadministered SCAN in 105 attendees at one primary-care practice Jordanova and colleagues (2004) devote almost all of their discussion to comments on what, in our opinion, is our quite different comparison of these instruments in 205 geographically sampled community subjects (Brugha et al. 1999a, 2001) ; they argue that we may have been unduly pessimistic in our view that neither lay diagnostic interview was adequately valid for use in population-based research because the design of our study may have led to an underestimate of the true validity of the two lay survey measures. A particular design difference for which our study is criticized is that we erred by excluding 467 householders with low scores on the CIS-R (total scores from 0 to 7; Brugha et al. 1999a), a point also noted earlier by Regier (2000). Using their data restricted to patients with CIS-R scores of 8 or above the CIS-R was shown to have much poorer agreement with SCAN for ‘any ICD-10 diagnosis ’. They acknowledge that both comparison studies were designed to increase study efficiency, in their study by interviewing primarycare attendees and in ours by excluding low community scorers (CIS-R scores of 0–7) ; they suggest that both studies are, therefore, limited in their generalizability to the general population and that better studies need to be designed and carried out that include random samples of low and high scorers on other screening questionnaires. We concluded that bias due to the absence of data on low scorers in our study was almost certainly small, having carefully conducted sensitivity analyses and considered the literature on community comparisons almost all of which concurred with our findings (Brugha et al. 1999a, b). We note that their criticism was conditional : ‘ for both the CIDI and the CIS-R, kappas for diagnoses and syndromes were generally similar for the whole sample and the subsample of 26 persons scoring 8 or over on the CIS-R psychiatric morbidity scale. However, where the level of agreement for the whole sample was in the moderate to good range, and the disorder was relatively prevalent, the kappa was dramatically lower for the subgroup of those scoring 8 or over on the CIS-R. ’ Thus, their criticism applied to one of many sets of analysis (the difference reported not being statistically significant). We further note that important information on cell frequencies, sensitivity and specificity was not reported for these subgroup analyses. However, we would agree that more general population data ought to be collected and analysed across the full range of mental illness probability in order to further reduce uncertainty; such an opportunity has since arisen from the Second National Household Survey carried out in collaboration with ONS in 2000 (Singleton et al. 2001) in which CIS-R and SCAN data were collected on subsamples stratified with respect to severity of mental disorder (Taub et al. 2005). These community data do permit us to compare agreement within one study in low and high scorers on screening tests in subjects randomly sampled throughout Great Britain. Selection for a clinician interview was based on screening questions for psychosis and for personality disorder (Singleton et al. 2001). Of 612 pairs of community interviews 250 were collected on randomly sampled adults who screened negative and 362 were on screen positives on one or both screening instruments. Chance corrected agreement (Cohen, 1968) for the presence or absence of any anxiety or depressive disorder comparing SCAN and the CIS-R in the whole sample was 0.39 (95% CI 0.29–0.49) ; it was 0.31 (95% CI 0.04–0.58) in respondents who screened negative for psychosis and personality disorder and ranged from Psychological Medicine, 2005, 35, 1089–1091. f 2005 Cambridge University Press Printed in the United Kingdom