False-positive microhematuria in dipsticks urinalysis caused by the presence of semen in urine

Objectives Positive readings of blood in dipstick urinalysis may indicate trauma or imbalance in hemostasis associated with drug treatment. We evaluated the possibility that the presence of semen in urine may cause false-positive hematuria. Design and methods Semen specimens obtained from 25 healthy men were directly applied on urine dipsticks for evaluation of the presence of blood. Isolated sperm cells and seminal fluid were also tested. Dipstick analyses were further performed with semen samples diluted in normal urine. Four healthy male volunteers provided urine samples before and immediately after having had sexual relationships. These samples were dipstick tested for the presence of blood. Results Semen, spermatozoa and seminal fluid gave false positive results for microhematuria following direct application of samples on dipsticks as well as after their suspension in urine (p< 0.00001). Three out of four postcoital urine specimens yielded positive results for blood. Conclusions In men, postcoital urine may be falsely “positive” for microhematuria. This may have implication on the management of male patients in emergency situations such as acute coronary syndromes.