Effect of the addition of a help question to two screening questions on specificity for diagnosis of depression in general practice: diagnostic validity study

Objective To determine the validity of two written screening questions for depression with the addition of a question inquiring if help is needed. Design Cross sectional validation study. Setting 19 general practitioners in six clinics in New Zealand. Participants 1025 consecutive patients receiving no psychotropic drugs. Main outcome measures Sensitivity, specificity, and likelihood ratios of the two screening questions, the help question, combinations of the screening and help questions, and diagnosis by general practitioners. Results The help question alone had a sensitivity of 75% (95% confidence interval 60% to 85%) and a specificity of 94% (93% to 96%). The positive likelihood ratio for the help question was 13.0 (9.5 to 17.8) and the negative likelihood ratio was 0.27 (0.17 to 0.44). The likelihood ratio for patients wanting help today was 17.5 (11.1. to 27.7). The general practitioner diagnosis had a sensitivity of 79% (65% to 88%) and a specificity of 94% (92% to 95%). Conclusion Adding a question inquiring if help is needed to the two screening questions for depression improves the specificity of a general practitioner diagnosis of depression.