Validating the Questionnaire to Verify Stroke-Free Status by Patient History and Physical Examination
Background and Purpose: The Questionnaire to Verify Stroke-Free Status (QVSFS) is an 8-item structured telephone interview designed to identify stroke-free individuals. Previously, the QVSFS was validated with medical record review to identify stroke status in a cohort with a low prevalence (7%) of stroke or TIA. The aim of this study was to evaluate the validity of the QVSFS using a face-to-face history and physical examination in a group with a higher prevalence of stroke. Methods: A research assistant administered the QVSFS to outpatients from VA stroke and general internal medicine clinics. Subjects were defined as QVSFS (-) if responses to all 8 questions were negative. Questions requiring clarification were noted. Neurologists, blinded to QVSFS scores, interviewed and recorded the NIH Stroke Scale in all subjects to determine stroke-free status, defined as no history or examination findings of previous TIA or stroke. Results: Ninety-one subjects were examined, mean age was 69 years, 98% were male. Twenty-five of the subjects were judged stroke-free by the examiners and 66 had a prior history of stroke (63) or TIA (3). The negative predictive value of the QVSFS was 0.93 with positive predictive value 0.86. No question required rephrasing in more than 3 subjects; only 12 subjects (13%) required rephrasing of at least one question. Years of education was not associated with need for question rephrasing. Conclusions: The QVSFS can effectively identify stroke-free individuals with a high degree of accuracy, even in a population including a large proportion of patients with prior stroke or TIA. Accuracy for identifying subjects with stroke is slightly lower but still high. The QVSFS is valid for interviewer administration but, because of the need for question clarification in some subjects, should be further evaluated before using self- or mail-completion.