The objectives of this were to determine the correlation of greater than or equal to 3 red blood cells per high-power field (RBCs/HPF) with a positive urine dipstick for blood and to identify clinically relevant factors than can influence this relationship.
The charts of women with positive blood urine dipsticks were reviewed from August 2012 to August 2013. The cohort of women was divided into 2 groups; those with urine with greater than or equal to 3 RBCs/HPF on microscopy and those without. Relevant clinical and demographic variables were extracted from the electronic medical record. Data analysis was conducted using SAS version 9.4 (SAS Institute, Cary, NC).
Most of the 203 patients eligible for analysis were Caucasian, and the total cohort had a mean age of approximately 62.8 years. Microscopy confirmed greater than or equal to 3 RBCs/HPF in 25.6% of the urine samples. A dipstick finding of moderate or large blood was significantly more likely to have greater than or equal to 3 RBCs/HPF on univariate and multivariable analyses (P < 0.001). Factors significantly associated with greater than or equal to 3 RBCs/HPF were increasing age, recurrent urinary tract infections, and urinary specific gravity of greater than 1.010.
Lower urinary specific gravities appear to be associated with underestimating microhematuria, likely owing to the underrepresentation of the true number of red blood cells. Urine dipstick indicators of moderate or large blood increase the likelihood the microscopy samples demonstrated greater than or equal to 3 RBCs/HPF. These findings suggest that clarification of microhematuria detection and evaluation guidelines should be considered, given both important clinical and economic consequences.