American Board of Internal Medicine (ABIM) Certification Practice Exam

How is hematuria defined?

1. Less than 3 erythrocytes/hpf

2. 3 to 10 erythrocytes/hpf

3. More than 3 erythrocytes/hpf

4. More than 10 erythrocytes/hpf

The correct answer is: More than 3 erythrocytes/hpf

Hematuria is defined as the presence of red blood cells in the urine, which can indicate a variety of underlying conditions. The definition is specifically based on the number of erythrocytes observed per high-power field (hpf) during microscopic examination of the urine sediment. The threshold for diagnosing hematuria is typically set at more than 3 erythrocytes per high-power field. This threshold is clinically significant because it helps to distinguish between normal variations and potential pathological conditions that require further investigation. For instance, occasional red blood cells may appear due to benign causes such as exercise or trauma, but a count above 3/hpf is suggestive of an underlying issue, which could range from urinary tract infections to more serious conditions such as nephrolithiasis or malignancy. In contrast, thresholds below this level are often considered normal or within the limits of variability. Therefore, the definition provided accurately captures the clinical standard for identifying hematuria and justifies why the answer provided is correct.