Interobserver agreement in the diagnosis of stroke type

Interobserver agreement is essential to the reliability of clinical data from cooperative studies and provides the foundation for applying research results to clinical practice. In the Stroke Data Bank, a large cooperative study of stroke, we sought to establish the reliability of a key aspect of stroke diagnosis: the mechanism of stroke. Seventeen patients were evaluated by six neurologists. Interobserver agreement was measured when diagnosis was based on patient history and neurologic examination only, as well as when it was based on results of a completed workup, including a computed tomographic scan. Initial clinical impressions, based solely on history and one neurologic examination, were fairly reliable in establishing the mechanism of stroke (ie, distinguishing among infarcts, subarachnoid hemorrhages, and parenchymatous hemorrhages). Classification into one of nine stroke subtypes was substantially reliable when diagnoses were based on a completed workup. Compared with previous findings for the same physicians and patients, the diagnosis of stroke type was generally more reliable than individual signs and symptoms. These results suggest that multicentered studies can rely on the independent diagnostic choices of several physicians when common definitions are employed and data from a completed workup are available. Furthermore, reliability may be less for individual measurements such as signs or symptoms than for more-complex judgments such as diagnoses.