Effects of diagnostic uncertainty and misclassification on hospital performance indicators for acute stroke care

Abstract

The Stroke Improvement National Audit Programme (SINAP), now replaced by the Sentinel Stroke National Audit Programme, was established to provide comparative data on hospital performance indicators for stroke, but comparisons are only valid if case ascertainment is complete. In Gateshead we compared initial results from SINAP with those from a pre-existing hospital stroke register, which ran independently for 11 months after SINAP's introduction in 2010, as well as with Hospital Episode Statistics (HES) data. Of 315 confi rmed acute stroke cases identifi ed from the three combined data sources, 96 (30%) were omitted from SINAP and 51 (16%) were missed by HES. Of 478 suspected strokes in the combined datasets, 214 were either misclassifi ed by HES or remained with uncertain diagnosis. These patients had much lower mortality and shorter hospital stays than those with confi rmed stroke. This diagnostic uncertainty could be an important source of uncontrolled variation in, or even a potential target for manipulation of, hospital performance indicators for stroke.