From the Guidelines
Yes, menstrual blood can indeed cause a high erythrocyte count on a urine microscopy and culture sensitivity (MCS) test, as the red blood cells from menstrual fluid can contaminate the urine sample and lead to falsely elevated erythrocyte counts. This phenomenon is acknowledged in the context of microhematuria, where the presence of red blood cells in the urine can be due to various factors, including gynecologic sources such as menstruation 1. According to the AUA/SUFU guideline on microhematuria, published in The Journal of Urology in 2020, clinicians should consider the source of microhematuria, including gynecologic causes, when interpreting urinalysis results 1.
When menstrual blood contaminates a urine sample, the red blood cells present in menstrual fluid will be detected during microscopic examination, potentially leading to falsely elevated erythrocyte counts. This is a common source of specimen contamination that can complicate the interpretation of urinalysis results. To avoid this interference, it's recommended to postpone urine collection until menstruation has ended when possible. If testing cannot be delayed, using a tampon before collection and carefully collecting a midstream sample after thorough cleansing of the genital area can help minimize contamination.
Key considerations for healthcare providers include:
- The timing of menstruation when interpreting urinalysis results showing high red blood cell counts
- Distinguishing between pathological hematuria and normal menstrual contamination
- The use of a risk classification system for patients with microhematuria, as outlined in the AUA/SUFU guideline, to guide further diagnostic evaluation and management 1. Healthcare providers should consider these factors to ensure accurate interpretation of urinalysis results and appropriate patient care.
From the Research
Erythrocyte Count on Urine MCS
- The presence of erythrocytes in urine can be an indicator of various conditions, including hematuria, which is the presence of blood in the urine 2, 3, 4, 5.
- Hematuria can be classified as either gross or microscopic, with microscopic hematuria being more common and often having benign causes such as urinary tract infections or benign prostatic hyperplasia 2, 4, 5.
- However, microscopic hematuria can also be a sign of more serious conditions, such as glomerulonephritis or urologic malignancy, and therefore requires further evaluation 3, 4, 5, 6.
- The evaluation of urinary erythrocyte morphology (UEM) can be useful in identifying patients with glomerular hematuria, with certain morphological aspects of urine red blood cells, such as dysmorphic RBCs or acanthocytes, being indicative of glomerular injury 3, 6.
- The sensitivity and specificity of UEM in diagnosing glomerular hematuria can vary, but it has been shown to have a high positive predictive value for diagnosing glomerular disease 3, 6.
Menses and Erythrocyte Count
- There is no direct evidence in the provided studies to suggest that menses can cause a high erythrocyte count on urine MCS.
- However, it is possible that menstrual blood could contaminate a urine sample, potentially leading to a false positive result for hematuria.
- It is essential to consider the clinical context and obtain a thorough medical history when interpreting the results of a urine MCS, including any potential sources of contamination or interference, such as menses 2, 4, 5.