Introduction: While the prevalence of microscopic hematuria (MH) in the general population remains high, the malignancy detection rate is low. Extensive workup may create unnecessary radiation and instrumentation. Multiple guidelines and nomograms have been published to help reduce excessive evaluations. This study aimed to review our institution’s malignancy detection rate, modelled using the revised 2021 AUA/SUFU Microhematuria guideline and Kaiser-Permanente Hematuria Risk Index (HRI).
Methods: Retrospective review of our microscopic hematuria database of 3,147 patients to analyze malignancy detection rate, stratified for the 2021 AUA guidelines and HRI risk categories. Patient inclusion was RBC = 3/hpf with completed fields for demographics, risk factors, and full work-up. Categorization of malignancy was further broken down into grade, stage, and type. Solid parenchymal tumors (SPT) were included if pathologically confirmed or highly suspicious on imaging. Patients who presented with MH but had a history of gross hematuria were stratified per AUA or HRI grouping. Statistical analysis was performed by area under receiver operating characteristic curves.
Results: 2,001 patients met inclusion criteria. Overall, 36 neoplasms were diagnosed after workup: 21 non-muscle invasive bladder cancer, 1 muscle-invasive bladder cancer, 2 upper tract urothelial cancers, 12 SPTs. AUA risk categories had a total positive detection rate of 0% (Low), 0.67% (Medium), and 2.83% (High). HRI score (0-11) showed malignancy detection rates of 0.97% (Low; 0-4), 2.65% (Moderate; 5-8), and 9.68% (High; 9-11). Looking only at urothelial malignancies (excluding SPT), the breakdown (AUA versus HRI respectively) was Low: 0 vs 0.18%, Medium/Moderate: 0.13 vs 2.28%, and High: 2.10 vs 9.68%. The HRI classified 1,139 patients as low-risk with 2 urothelial malignancies detected (0.18%), while the AUA classification only included 163 patients (0%). The HRI score stratification urothelial detection area under the curve for ROC was 0.812 compared to 0.709 (AUA).
Conclusions: After stratifying our database population based on the 2021 AUA/SUFU Guideline and Kaiser-Permanente HRI, we found that both groups had linear increases in malignancy detection rates with increasing risk group. However, the HRI, which uses a more granular categorization, would have avoided unnecessary workup in a significantly higher proportion of patients. Future directions should analyze further sub-stratification to create a more specific nomogram that avoids unnecessary workup.
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