Reliability and validity of urinary nerve growth factor measurement in women with lower urinary tract symptoms

INTRODUCTION AND HYPOTHESIS - The validity and reliability of measurement of urinary NGF as a diagnostic biomarker in women with lower urinary tract dysfunction (LUTD) is uncertain. We aimed to evaluate both the diagnostic and discriminant validity, and the test-retest reliability of urinary NGF measurement in women with LUTD.

METHODS - Urinary NGF was measured in women with LUTD (n = 205) and asymptomatic subjects (n = 31). Urinary NGF was assayed using an ELISA method and normalized against urinary creatinine. NGF/creatinine ratios were compared between symptom subgroups using Mann-Whitney U test, and between different urodynamic diagnoses using the Kruskal-Wallis test. Receiver Operator Characteristic (ROC) analysis was employed to evaluate the diagnostic performance of urinary NGF. Test-retest reliability of NGF measurement was assessed using intra-class correlation (ICC).

RESULTS - Urinary NGF was significantly but non-specifically increased in symptomatic patients when compared to controls (13.33 vs. 2.05 ng NGF/g Cr, P < 0.001). On multivariate logistic regression NGF was a good predictor of patients having OAB or not, however, the adjusted odds ratio only 1.006. ROC analysis demonstrated poor discriminant ability between different symptomatic groups and urodynamic groups. Using a cut off of 13.0 ng NGF/g creatinine the test provides a sensitivity of 81%, but a specificity of only 39% for overactive bladder. The assays demonstrated good test-retest reliability with ICC of 0.889.

CONCLUSIONS - Although urinary NGF can be reliably assayed, and is increased in various LUTDs, it discriminates poorly between these disorders therefore has very limited potential as a biomarker. Neurourol. Urodynam. © 2015 Wiley Periodicals, Inc.

Neurourol Urodyn. 2015 Jul 30. doi: 10.1002/nau.22832. [Epub ahead of print]

Vijaya G1, Cartwright R2, Bhide A1, Derpapas A3, Fernando R3, Khullar V4.

1 St. Mary's Hospital-Department of Urogynaecology, London, United Kingdom.
2 Imperial College London-Institute of Reproductive and Developmental Biology, London, United Kingdom.
3 St. Mary's Hospital, Imperial College Healthcare NHS Trust-Urogynaecology, London, United Kingdom.
4 St. Mary's Hospital-Urogynaecology Ground Floor, Cambridge Wing St. Marys Hospital, London, United Kingdom.