Blood coagulation (clotting) abnormalities (coagulopathies) are a rare cause of ischemic stroke. Doctors typically suspect that hypercoagulation (blood thickening) may be the cause of ischemic stroke only when no other cause is obvious. In fact, nearly one-third of specialized tests for coagulation disorders that doctors order for stroke patients are unlikely to affect their treatment decisions, concludes a study supported by the Agency for Healthcare Research and Quality (National Research Service Award training grant T32 HS00079). In this study, for example, these tests were ordered for patients who already had other indications for anticoagulation (blood-thinning) therapy with warfarin or for patients with contraindications to receiving warfarin.
Because of the high cost (about $1,000 for a battery of tests for hereditary coagulation defects alone) and low diagnostic yield of coagulation tests, as well as the low prevalence of coagulopathies in ischemic stroke, patients should be carefully selected for testing, conclude the Duke University researchers who conducted the study. They examined the medical records of 674 adult ischemic stroke patients admitted to an academic medical center over 3 years to identify factors associated with coagulation testing.
Of the 31 percent of patients tested for coagulopathies, 29 percent were tested when the result was unlikely to influence treatment decisions; in other words, 29 percent of these tests were inappropriate. For example, the most common manifestation of a coagulopathy is venous thrombosis (blockage of a vein) or a history of miscarriage. However, neither of these risk factors was consistently documented in the patients' medical records, and neither significantly influenced testing status. Overall, age was the only clinical factor increasing the likelihood of a coagulopathy that appeared to influence ordering of specialized coagulation tests. Young patients with ischemic stroke are more likely to have a coagulopathy, even though this still accounts for only 10 to 15 percent of stroke cases in this group.
Details are in "Use of specialized coagulation testing in the evaluation of patients with acute ischemic stroke," by Cheryl Bushnell, M.D., Zaeem Siddiqi, M.D., Ph.D., Joel C. Morgenlander, M.D., and Larry B. Goldstein, M.D., in the March 2001 Neurology 56, pp. 624-627.
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