Predicting urinary creatinine excretion and its usefulness to identify incomplete 24h urine collections

• Published in: British journal of nutrition Vol. 108; no. 6
• Main Authors: Keyzer, W., de, Huybrechts, I, Dekkers, A.L.M, Geelen, A, Crispim, S.P, Hulshof, P.J.M, Andersen, L.F, Rehurkova, I, Ruprich, J, Volatier, J.L, Maele, G., van, Slimani, N, Veer, P., van 't, Boer, E., de, Henauw, S., de
• Format: Journal Article
• Language: English
• Published: 28.09.2012
• Subjects: 4-aminobenzoic acid; completeness; diet; european centers; potassium; protein; recalls; sodium; stability; validation
• ISSN: 0007-1145; 1475-2662
• DOI: 10.1017/S0007114511006295

Studies using 24 h urine collections need to incorporate ways to validate the completeness of the urine samples. Models to predict urinary creatinine excretion (UCE) have been developed for this purpose; however, information on their usefulness to identify incomplete urine collections is limited. We aimed to develop a model for predicting UCE and to assess the performance of a creatinine index using para-aminobenzoic acid (PABA) as a reference. Data were taken from the European Food Consumption Validation study comprising two non-consecutive 24 h urine collections from 600 subjects in five European countries. Data from one collection were used to build a multiple linear regression model to predict UCE, and data from the other collection were used for performance testing of a creatinine index-based strategy to identify incomplete collections. Multiple linear regression (n 458) of UCE showed a significant positive association for body weight (ß = 0·07), the interaction term sex × weight (ß = 0·09, reference women) and protein intake (ß = 0·02). A significant negative association was found for age (ß = - 0·09) and sex (ß = - 3·14, reference women). An index of observed-to-predicted creatinine resulted in a sensitivity to identify incomplete collections of 0·06 (95 % CI 0·01, 0·20) and 0·11 (95 % CI 0·03, 0·22) in men and women, respectively. Specificity was 0·97 (95 % CI 0·97, 0·98) in men and 0·98 (95 % CI 0·98, 0·99) in women. The present study shows that UCE can be predicted from weight, age and sex. However, the results revealed that a creatinine index based on these predictions is not sufficiently sensitive to exclude incomplete 24 h urine collections.