What is Gross Hematuria? The correlation between Gross and Microscopic Hematuria Peter Peacock, M.D., Albert Einstein Medical Center Abstract presented at PaACEP 1998 Hypothesis: Gross hematuria is insensitive for detecting the degree of microscopic hematuria (>100 rbc/hpf) that may mandate genitourinary imaging studies in blunt trauma. Methods: One examiner prepared samples daily by serially diluting his blood (Hb=14.9-15.9) in his urine (clear yellow, 0 rbcs/hDf, sg 1.012 - -93). A range of 10 dilutions (0-100 ul blood/10 ml urine) was chosen to represent the range of appearances of gross hematuria. Ranges of rbcs/hpf were determined by performing laminar flow microscopy on 10 separately prepared samples for each dilution. 222 trauma clinicians (14 nurses, 24 surgical residents, 11 surgical attendings, 101 EM residents, 39 EM attendings, 33 medical students) in 5 trauma centers were asked during trauma conferences to participate and all agreed. Blinded to samples' compositions, clinicians individually rated the presence/absence of gross hematuria in each sample. Samples were provided in random order under normal zoom lighting. Results: The table shows microscopy and positive responses (sensitivity), including 95% confidence intervals (CI) calculated by exact methods, for selected dilutions. No differences in response rates for any dilutions were found between types of providers (p > 0.08, all comparisons, Cochran's Q test). Conclusion: Within 95% confidence intervals,' the maximum possible sensitivity of gross hematuria for detecting >= 750 rbcs/hpf is 78%. Absence of gross hematuria does not rule out a degree of microscopic hematuria that may mandate genitourinary imaging in blunt trauma. blood/ml urine rbc/hpf # pos. % pos. 95% C.I. 0 ul 0 8/444 1.8% 0.8% to 3.5% 1 ul <100 3/222 1.4% 0.3% to 3.9% 2.5 ul 156-200 9/222 4.1% 1.9% to 7.6% 20 ul 788-1237 160/222 72.11 66.2% to 78.0% 50 ul 2680-3850 216/222 97.3% 94.2% to 99.0% 100 ul 6750-7570 221/222 99.6% 97.5% to 100%