Impact of the International Continence Society (ICS) report on the standardisation of terminology in nocturia on the quality of reports on nocturia and nocturnal polyuria: a systematic review.

Objective: To systematically review and evaluate the impact of the International Continence Society (ICS)-2002 report on standardisation of terminology in nocturia, on publications reporting on nocturia and nocturnal polyuria (NP). In 2002, the ICS defined NP as a Nocturnal Polyuria Index (nocturnal urine volume/total 24-h urine volume) of >0.2-0.33, depending on age.

Materials And Methods: In April 2013 the PubMed and Embase databases were searched for studies (in English, German, French or Dutch) based on original data and adult participants, investigating the relationship between nocturia and NP. A methodological quality assessment was performed, including scores on external validity, internal validity and informativeness. Quality scores of items were compared between studies published before and after the ICS-2002 report.

Results: The search yielded 78 publications based on 66 studies. Quality scores of studies were generally high for internal validity (median 5, interquartile range [IQR] 4-6) but low for external validity. After publication of the ICS-2002 report, external validity showed a significant change from 1 (IQR 1-2) to 2 (IQR 1-2.5; P = 0.019). Nocturia remained undefined in 12 studies. In all, 19 different definitions were used for NP, most often being the ICS (or similar) definition: this covered 52% (n = 11) of studies before and 66% (n = 27) after the ICS-2002 report. Clear definitions of both nocturia and NP were identified in 67% and 76% before, and in 88% and 88% of the studies after the ICS-2002 report, respectively.

Conclusion: The ICS-2002 report on standardisation of terminology in nocturia appears to have had a beneficial impact on reporting definitions of nocturia and NP, enabling better interpretation of results and comparisons between research projects. Because the external validity of most of the 66 studies is considered a problem, the results of these studies may not be validly extrapolated to other populations. The ICS definition of NP is used most often. However, its discriminative value seems limited due to the estimated difference of 0.6 nocturnal voids between individuals with and without NP. Refinement of current definitions based on robust research is required. Based on pathophysiological reasoning, we argue that it may be more appropriate to define NP based on nocturnal urine production or nocturnal voided volumes, rather than on a diurnal urine production pattern.