Simple Urine Test to Evaluate Adherence to Oral 5-ASA in Teenagers With Ulcerative Colitis: Proof of Concept.
5-Aminosalicylic acid (5-ASA) is an important maintenance drug for patients with ulcerative colitis. A proportion of the ingested dose is excreted in the urine. Measuring 5-ASA and its metabolites in urine requires mass spectrometry, which is not widely available for this purpose. Urinary 5-ASA can be measured by colorimetry using the serum salicylic acid assay and is a surrogate marker of recent 5-ASA ingestion. We evaluated whether measuring 5-ASA in first morning voids or in random spot urine samples correctly identifies teenagers with poor adherence to oral 5-ASA.



Teenagers who were prescribed a current regimen including >40 mg · kg · day of 5-ASA were invited to collect their spot urine with various time lapses since their last presumed 5-ASA ingestion. Classification of adherence was based on a composite method that included a patient-reported adherence scale and 6-thioguanine levels in erythrocytes.



Teenagers who were classified as "good adherers" had 66 of 69 (96%; 95% confidence interval 87%-99%) spot urine samples with detectable 5-ASA levels. "Poor adherers" had 30 of 45 (67%; 95% confidence interval 52%-79%) spot urine samples with undetectable 5-ASA levels. The "good adherers" with false-negative urine tests were on a once daily dosing regimen and had collected a spot urine sample shortly before the next dosage. Their first morning voids had detectable 5-ASA levels.



Undetectable 5-ASA levels in the first morning void confirms short-term nonadherence to oral 5-ASA.
*Department of Pediatric Gastroenterology †Department of Clinical Pharmacy and Pharmacology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
Alie
A
Dijkstra
Daan J
DJ
Touw
Patrick F
PF
van Rheenen
D000284:Administration, Oral; D000293:Adolescent; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000627:therapeutic use* / Q000652:urine*; D016022:Case-Control Studies; D002648:Child; D003093:Colitis, Ulcerative / Q000188:drug therapy* / Q000652:urine; D004334:Drug Administration Schedule; D005260:Female; D006801:Humans; D008297:Male; D055118:Medication Adherence; D019804:Mesalamine / Q000627:therapeutic use* / Q000652:urine*; D000075082:Proof of Concept Study; D011446:Prospective Studies
D000894:Anti-Inflammatory Agents, Non-Steroidal; D019804:Mesalamine