title: Performance of the 6-item Kessler scale for measuring serious mental illness in Hong Kong.
abstract: BACKGROUND
  The 6-item Kessler scale (K6) promises to be a valuable epidemiological tool for assessing serious mental illness (SMI) in communities with limited resources for psychiatric research and treatment. Its performance in Chinese community has not been studied with reference to clinically assessed SMI.
  
  
  METHODS
  From a representative telephone-based population survey (n = 3014) that administered the K6, 153 participants were readministered the K6 and, on the same day, interviewed face-to-face by clinicians using the Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorder, Fourth Edition, Axis I Disorder. Predictive indicators such as McNemar χ(2), area under receiver operating characteristic curve and stratum-specific likelihood ratios were used to investigate the concordance between the K6 and clinical status of SMI, individual-level predicted probabilities of having SMI, and the weighted prevalence of SMI in the community.
  
  
  RESULTS
  The K6 exhibited high internal consistency and test-retest reliability. Factor analysis revealed 2 correlating components composed of depression and anxiety. Matching of K6 caseness and SMI status showed that at the cutoff of 12/13, the area under receiver operating characteristic curve was moderate (0.69). The K6 had high specificity and was a stronger screen-out than screen-in tool for SMI. The weighted prevalence estimate of SMI in Hong Kong was 6.5%. A person scoring 13 or above on the K6 has a probability of at least 22.2% of having SMI.
  
  
  CONCLUSIONS
  The Chinese K6 is reliable and generates the likelihood of SMI with substantial concordance with face-to-face clinical interviews in Hong Kong. It is a valuable tool for screening SMI, behavioral risk factor surveillance, and community epidemiological surveys.
authors: Department of Psychiatry, The Chinese University of Hong Kong, Hong Kong SAR. singlee@cuhk.edu.hk
authors: Sing
authors: S
authors: Lee
authors: Adley
authors: A
authors: Tsang
authors: King Lam
authors: KL
authors: Ng
authors: Yee Ling
authors: YL
authors: Ma
authors: Wanjun
authors: W
authors: Guo
authors: Arthur
authors: A
authors: Mak
authors: Kathleen
authors: K
authors: Kwok
mesh_terms: D000328:Adult; D005163:Factor Analysis, Statistical; D005260:Female; D006306:Health Surveys; D006723:Hong Kong / Q000453:epidemiology; D006801:Humans; D007406:Interview, Psychological; D016013:Likelihood Functions; D008297:Male; D008403:Mass Screening / Q000379:methods*; D011159:Population Surveillance / Q000379:methods*; D015995:Prevalence; D011569:Psychiatric Status Rating Scales; D011594:Psychometrics; D011618:Psychotic Disorders / Q000453:epidemiology / Q000517:prevention & control*; D015203:Reproducibility of Results; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D016037:Single-Blind Method