Criterion-Related Validity of the 9 Questions Depression Rating Scale revised for Thai Central Dialect

Abstract

Objective : To study criterion related validity of the 9 Questions Depression Rating Scale-revised for
Thai Central dialect in term of sensitivity, specificity and predictive validity
Method : The diagnostic test study design was conducted by comparing the 9Q with psychiatrist’s
diagnosis as the gold standard during January to April 2017. Samples recruited from Thai Central
population who aged above 15 years old. Cluster stratified random sampling by age and sex was
performed to select 1,164 participants who living in Nakornnayok, Nonthaburi, and Ayuthaya province.
Participants were informed consent before receiving interview by psychiatric nurses using demographic
questionnaire, the 9 Questions Depression Rating Scale-revised for Thai Central dialect (9Q), and
the Hamilton rating scale for depression (HRSD). Then they were interviewed by a psychiatrist who
was blind the test result, and using the Mini international neuropsychiatric interview Thai version for
diagnosis. Descriptive statistics were used for demographic data and inferential statistics were used
for sensitivity, specificity, cut off point, Pearson Correlation Coefficient และ ROC curve with 95%
confidence interval.
Results : Of 1,164 participants, 63.8% of them was female, mean aged of 39.15 (SD 18.75) years,
56.4% had low educational level (less than 12 year), 35.3% was labor, and 33% having physical
illness. Prevalence of depressive disorder was 5.58% which classified to Major depressive disorder
of 3.87%, Dysthymia of 2.75%. Mean scores of 9Q was 4.56 (SD 7.65) while mean score of HRSD
depression was 3.72 (SD 4.48. Correlation scores between 9Q and HRSD was calculated Pearson’s
product-moment correlation of 0.719 (95% CI: 0.690 to 0.746). Optimum cut-off point of 9Q was 7
and above with sensitivity of 86.15, specificity of 83.12, correct classified of 83.29, positive likelihood
ratio of 5.10, and ROC area of 0.897 (95%CI 0.850 to 0.943). Range of 9Q scores were classified
severity of depression as the following : 7-12 as mild degree with sensitivity of 86.2%, specificity of
83.1%, positive likelihood ratio of 5.1; 13-17 as moderate with sensitivity of 83.3%, specificity of 93.2%,
positive likelihood ratio of 12.2; 18 and above as severe with sensitivity of 80.0%, specificity of 95.2%,
positive likelihood ratio of 16.6
Conclusion : The 9 Questions Depression Rating Scale-revised for Thai Central Dialect has good
criterion related validity. Optimum cut-off point of 9Q was 7 and above with high sensitivity,
high specificity. It might be used in primary health care centers for surveillance system of depressive
disorders in Thailand.