Reliability of spot samples for assessment of urinary excretion of pyridinoline in patients with rheumatoid arthritis.
OBJECTIVE
To determine how well a spot urine sample of patients with active rheumatoid arthritis (RA) can predict 24-hour urinary pyridinoline and deoxypyridinoline excretion.


METHODS
Urine samples of 11 hospitalized RA patients taken on 2 consecutive days at 8 a.m. and 4 p.m. were compared with samples from 24-hour collections (gold standard). High-performance liquid chromatography was used to measure the collagen crosslink concentrations.


RESULTS
Sampling time was the only significant factor (repeated measurement ANOVA). Significant differences were found between morning and 24-hour samples and between morning and afternoon samples, but not between afternoon and 24-hour samples.


CONCLUSIONS
Samples collected in the afternoon (4 p.m.) give the best approximation of 24-hour urinary pyridinoline excretion in patients with active rheumatoid arthritis. In longitudinal studies the sampling time should be fixed.
Internal Medicine/Rheumatology Department, Maastricht University Hospital, Maastricht, The Netherlands.
A C
AC
Verhoeven
M
M
Boers
J M
JM
te Koppele
W H
WH
van der Laan
J
J
de Roos
S
S
van der Linden
D000328:Adult; D000368:Aged; D000596:Amino Acids / Q000652:urine*; D000704:Analysis of Variance; D001172:Arthritis, Rheumatoid / Q000473:pathology* / Q000652:urine*; D002940:Circadian Rhythm; D003404:Creatinine / Q000652:urine; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D013997:Time Factors
D000596:Amino Acids; C015484:pyridinoline; C036020:deoxypyridinoline; D003404:Creatinine