Tiredness

This article overstates the value of the two questions in diagnosing
depression.

The authors state that "A positive answer to either question suggests
depression." when in reality far more patients responding positively will
not have depression.

The original research by Arroll.B et al showed a high sensitivity
(97%) but a low positive predictive value (PPV) (18%)and the post-test
probabilities were that there would be 5 false-positives for each true-
positive.

This does not mean that the two questions are of no value as the high
sensitivity means that they are an excellent method for excluding
depression as the cause of tiredness. The chances of a patient with a
negative test having depression are only 0.3%.

Without clarification of the PPV of this approach there is a danger
that patients will be labelled as depressed incorrectly and more serious
illness may be missed.

Reference

Arroll B, Khin N,Kerse N (2003) Screening for depression in primary
care with two verbally asked questions: cross sectional study BMJ
2003;327:1144-1146 (15 November)

Competing interests:
None declared