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February 2, 1994

Users' Guides to the Medical Literature: III. How to Use an Article About a Diagnostic Test A. Are the Results of the Study Valid?

Author Affiliations

Reprint requests to McMaster University Health Sciences Centre, 1200 Main St W, Room 2C12, Hamilton, Ontario, Canada L8N 3Z5 (Dr Guyatt).
From the Departments of Medicine and Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Ontario.

JAMA. 1994;271(5):389-391. doi:10.1001/jama.1994.03510290071040

CLINICAL SCENARIO  You are a medical consultant asked by a surgical colleague to see a 78-year-old woman, now 10 days after abdominal surgery, who has become increasingly short of breath over the last 24 hours. She has also been experiencing what she describes as chest discomfort, which is sometimes made worse by taking a deep breath (but sometimes not). Abnormal findings on physical examination are restricted to residual tenderness in the abdomen and scattered crackles at both lung bases. Chest roentgenogram reveals a small right pleural effusion, but this is the first roentgenogram since the operation. Arterial blood gases show a Po2 of 70 mm Hg, with a saturation of 92%. The electrocardiogram shows only nonspecific changes.You suspect that the patient, despite receiving 5000 U of heparin twice a day,

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