Influencing factors on the NMP-22 urine assay: an experimental model

Pooled urine from healthy subjects were spiked with varying concentrations of benign (UROtsa) cells, cancer cells (RT4, T24, KU-7 and UM-UC-14), whole blood or serum, prior to analysis with both NMP22？ Bladder Cancer ELISA test and the NMP22？ BladderChek？ point-of-care test.Urines from control subjects were negative for NMP-22. The addition of whole blood at 50ul/10？ml, but not serum, resulted in a false-positive result. Furthermore, the addition of a high concentration of benign urothelial cells (106) or the cell lysate from these cells (306？μg protein) resulted in a false-positive result. High concentrations of pooled-cancer cells (106) or cell lysate (30.6？μg and above) resulted in a positive NMP-22 assay. Concordance between the NMP-22 ELISA assay and the NMP-22 point of care assay was >90%.Rather than detecting a specific tumor antigen, urinary NMP-22 assays may be measuring the cellularity or amount of cell turnover that may be introduced into the urine by a variety of conditions, including surface shedding from bladder tumors. The absence of significant urinary cellularity in some cases due to lesion characteristics or the timing of sampling may result in false-negative NMP-2 assays.Non-invasive urine tests for the early detection or post-surgical surveillance of bladder cancer (BCa) are highly desirable for both patient and healthcare system. Currently, voided urinary cytology (VUC) is the most widely used non-invasive urine test, with reported sensitivities ranging from 13–75% and specificities ranging from 85–100% [1,2]. A couple of single-biomarker urinalysis assays have been developed for use in this context. One is the bladder tumor antigen (BTA) test, which detects urinary complement factor H-related proteins using monoclonal antibodies [3]. Two assay formats, BTA stat？ and BTA TRAK？ (Polymedco Inc. Cortlandt Manor, NY, USA), are FDA approved for the detection and surveillance of BCa in urine samples. For BCa detection, urinary BTA tests have diagnosti