Cutoff value of urinary arginine vasopressin for nocturnal polyuria in elderly men.

OBJECTIVES

To determine the cutoff value of early-morning urinary arginine vasopressin (uAVP)/urinary creatinine (uCr) for patients with nocturnal polyuria (NP), and to investigate whether abnormal secretion of AVP at nighttime is a risk factor of NP in elderly men.

METHODS

A total of 189 men older than 50 years of age with nocturia were enrolled. The frequency volume chart was recorded. The uAVP, urinary sodium, uCr, and osmolarity of a single urine sample voided at 6:00 am were measured in all cases. Two definitions of NP--nocturnal urine volume/24-hr production greater than 0.35 (NP index [NPI] definition) and a nocturnal urine volume of 0.9 mL/min x the sleeping duration or greater (NUV definition)--were used for analysis.

RESULTS

uAVP/uCr was an independent predictor for NP according to the NPI and NUV definitions. The cutoff value of uAVP/uCr for NP was 23.4 pg/mL/Cr according to the NPI definition and 28.3 pg/mL/Cr according to the NUV definition. The sensitivity of the cutoff value according to the NPI and NUV definitions was 69% and 77%, respectively, and the specificity was 61% and 66%, respectively. In both NP definitions, 31% and 38% of the patients with a uAVP/uCr greater than the cutoff value showed NP. Significant differences in NUV and urine osmolarity, but not in uAVP/uCr and uNa/uCr, between the NP group and the non-NP group were found using both NP definitions.

CONCLUSIONS

We demonstrated that age and uAVP/uCr were independent predictive factors for nocturia in patients with NP. The cutoff value of uAVP/uCr is a useful screening marker for NP in elderly men with nocturia.