The systematic review by Watson and Pignone tells us which diagnostic tools accurately detect late life depression in primary care. Their methodology is robust enough for us to be confident that the 15 item GDS, CES-D, and SelfCARE(D) are reliable instruments, confirming widespread clinical practice in specialist settings. The choice of tool lies with the physician, who might sensibly copy local colleagues, especially when referral pathways make the use of common instruments helpful.

Some questions remain unanswered. Do primary care physicians actually use such instruments? Recognition of depression in primary care may occur in different ways.¹ These 3 instruments may have a secondary role of confirming suspected depression in selected patients. Primary care physicians in gatekeeping roles will rightly avoid screening entire subgroups given that evidence to support such use of tools is minimal.

How do we identify and manage the more common forms of subsyndromal depression? The 3 reliable instruments accurately detect only major depression, which affects about 2% of older people. Unfortunately, up to 20% of this group have levels of depressive symptoms below the threshold for diagnosis, yet experience substantial morbidity and loss of function. The diagnostic task of distinguishing depression from dementia is also a problem.

Management options may be more important than reliable diagnosis in influencing the behaviour of primary care physicians. Backward reasoning encourages us to identify only conditions that we can treat. Evidence of effectiveness of interventions for major depression is reasonably good, at least compared with that for minor depression and other depressive disorders of later life,² and so the 3 tools are worth including in our diagnostic repertoire.