Urine levels of nerve growth factor (NGF) fluctuate in line with changes in bladder pathophysiology, a 5-year study of people with overactive bladder (OAB) has found.
The results contradict the generally held belief in clinical practice that urinary NGF is not a useful biomarker of disease severity or a viable alternative to urodynamic studies.
Hann-Chorng Kuo (Buddhist Tzu Chi General Hospital, Hualien City, Taiwan) recruited 75 patients (30 women, mean age 73.5 years) with OAB and for whom serial NGF results were available over at least a 5-year period.
All participants were assessed for bladder condition (ie, OAB dry or wet), level of urgency and urodynamic diagnosis (ie, normal, increased bladder sensation [IBS], or detrusor overactivity [DO]).
Over the 5-year study period, 42.7% of the participants showed an improvement in their bladder condition, changing either from OAB-dry to IBS/normal or from OAB-wet to OAB-dry/IBS/normal.
A further 14.6% of participants showed a deterioration in their condition, with symptoms changing from OAB-dry to OAB-wet, while the remainder had a stable diagnosis.
Writing in the Journal of Urology, Kuo et al report that urinary levels of NGF normalised by the concentration of urinary creatinine (NGF/Cr) were not correlated with the change in bladder condition, whether based on OAB subtype or urgency severity score.
Between baseline and 5 years, however, urinary NGF/Cr levels fell significantly (from 0.94 to 0.17 pg/mg) in patients with an improved urodynamic diagnosis, increased significantly (from 0.55 to 2.08 pg/mg) in patients with a worsened urodynamic diagnosis and were relatively unchanged (from 0.98 to 0.97 pg/mg) in patients with stable urodynamics.
Furthermore, urinary NGF/Cr levels rose by a nonsignificant amount (from 0.63 to 1.98 pg/mg) in patients whose urodynamic diagnosis changed from non-DO to DO, and decreased significantly (from 0.65 to 0.15 pg/mg) in patients who changed from DO to non-DO.
In multiple linear regression analysis, the change in urodynamic diagnosis was a significant predictor of change in urinary NGF/Cr levels.
Noting that OAB is a dynamic syndrome and that the specific OAB diagnosis may change over time, the authors conclude: “The urinary NGF levels reflect changes in bladder conditions according to the urodynamic findings.”
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