Diagnostic accuracy of NMP 22 and urine cytology for detection of transitional cell carcinoma urinary bladder taking cystoscopy as gold standard: Diagnostic accuracy of NMP 22 in TCC Urinary Bladder

Objective: To determine diagnostic accuracy of NMP 22 and urine cytology in the detection of transitional cell carcinoma (TCC) urinary bladder taking cystoscopy as a gold standard in patients having provisional diagnosis of bladder cancer (BC).

Methods: This cross sectional validational study enrolled 380 patients fulfilling selection criteria and was conducted at Armed Forces Institute of Urology (AFIU) Rawalpindi, Pakistan form July 2018 to July 2019. The urine sample collected underwent NMP22 and cytological analysis followed by rigid cystoscopy. Reports of all three tests divided patients into positive or negative for malignancy as per defined criteria. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and diagnostic accuracy of NMP 22, urine cytology and their combination was determined. Receiver operating characteristic (ROC) curve analysis performed and area under the curve (AUC) compared among these tests.

Results: The average age of patients was 53.08 ± 12.41 years having male to female ratio 3.75:1(300 males and 80 females). NMP 22 had better sensitivity and comparable specificity to cytology (81.9 & 81.2% vs 54 & 93.9%). Combination of NMP 22 / cytology outperformed both in terms of sensitivity (91.63 vs 81.83 vs 53.96), NPV (87.59 vs 77.46 vs 61.02) and diagnostic accuracy (85.26 vs 81.58 vs 71.32) but at the cost of specificity (76.97 vs 81.21 vs 93.94) and PPV (83.83 vs 85.02 vs 92.06). ROC curve revealed statistically significant higher AUC (0.843 vs .815 vs .73) for combination as compared to NMP 22 and Cytology (p<0.001).

Conclusion: NMP22 is a quick, point of care test having higher sensitivity, NPV and accuracy but similar specificity and PPV to urine cytology for detection of TCC urinary bladder. Combination outperformed both in terms of sensitivity while having modest specificity.