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Reference values for the nocturnal bladder capacity index
Author(s) -
Burton Claire,
Weiss Jeffrey P.,
Parsons Matthew,
Blaivas Jerry G.,
Coats Alfred C.
Publication year - 2011
Publication title -
neurourology and urodynamics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.918
H-Index - 90
eISSN - 1520-6777
pISSN - 0733-2467
DOI - 10.1002/nau.20924
Subject(s) - nocturia , medicine , asymptomatic , cutoff , lower urinary tract symptoms , nocturnal , urology , population , overactive bladder , urinary system , pathology , prostate , physics , alternative medicine , environmental health , quantum mechanics , cancer
Aims The Nocturnal Bladder Capacity Index (NBCi) has been reported to be useful in distinguishing between nocturia caused by low bladder capacity and nocturnal polyuria. This paper aims to calculate reference values for NBCi from an asymptomatic population by comparing these with NBCi values from patients with lower urinary tract symptoms (LUTS) to obtain an indication of the sensitivity with which the NBCi detects low nocturnal bladder capacity. This paper also compares the sensitivity of rounded and unrounded calculations of NBCi. Methods Computer processed 3‐day bladder diaries from 253 asymptomatic volunteers and 184 female patients with LUTS were analyzed. NBCi values were calculated from each diary using rounded and unrounded formulae. 90th and 95th centile NBCi cutoff values were obtained from frequency distributions. Results NBCi reference values from the asymptomatic group were 1.1 (unrounded) and 0.7 (rounded) for 90th centile, and 1.3 (unrounded) and 1.0 (rounded) for 95th centile. The use of the rounded formula gave identical NBCi values despite a large variation in V n /V max ratios whereas unrounded NBCis varied continuously with V n /V max ratios. The unrounded formula found significantly more elevated NBCis in the patient group. Conclusion We suggest that an unrounded NBCi of 1.3 be considered a cutoff point above which reduced nocturnal bladder capacity should be investigated as a cause of nocturia. Rounding the NBCi lead to an underestimation of elevated values in a population of female patients with LUTS. Neurourol. Urodynam. 30:52–57, 2011. © 2010 Wiley‐Liss, Inc.