{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,8,27]],"date-time":"2025-08-27T16:10:03Z","timestamp":1756311003554,"version":"3.44.0"},"reference-count":12,"publisher":"BMJ","issue":"6","content-domain":{"domain":["bmj.com"],"crossmark-restriction":true},"short-container-title":["BMJ Case Rep"],"accepted":{"date-parts":[[2020,5,30]]},"published-print":{"date-parts":[[2020,6]]},"abstract":"<jats:p>\u200bSerum concentrations of paracetamol are measured to investigate the cause of acute hepatitis, monitor the clearance of paracetamol from the body and to determine if supratherapeutic levels warrant treatment with N-acetylcysteine (NAC). \u200bA 49-year-old man treated for ischaemic colitis developed worsening renal and liver function tests. As part of the investigation of hepatorenal failure, paracetamol levels were requested, which were elevated at 14 mg\/L (normal &lt;4 mg\/L) resulting in treatment with NAC. Despite treatment, levels of paracetamol remained elevated and the link between hyperbilirubinemia and false-positive paracetamol levels was identified. \u200bBilirubin and its by-products have intense absorbance in the ultraviolet and visible regions of the electromagnetic spectrum, causing interference in the enzymatic colorimetric assay most commonly used to measure paracetamol concentration, resulting in false-positive paracetamol levels. Laboratories correct for this interference above a predetermined bilirubin concentration, termed the Icteric Index; however, in our case this interference occurred at a lower level of hyperbilirubinaemia than previously identified as significant. This interaction was found to be more significant at lower bilirubin levels when low or no paracetamol levels were present in the serum, resulting in a change to laboratory practice and development of a \u2018Sliding Scale\u2019 approach to analysis. \u200bConcurrent bilirubin or Icteric Index measurement is recommended for all laboratories that use the enzymatic colorimetric assay for paracetamol measurement. Lower Icteric Index or bilirubin thresholds are required when low or no paracetamol levels are present in the serum to prevent false-positive paracetamol results. We describe a new \u2018Sliding Scale\u2019 approach to analysis, and highlight an important interaction for clinicians to be aware of.<\/jats:p>","DOI":"10.1136\/bcr-2020-234702","type":"journal-article","created":{"date-parts":[[2020,6,30]],"date-time":"2020-06-30T15:55:10Z","timestamp":1593532510000},"page":"e234702","update-policy":"https:\/\/doi.org\/10.1136\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":1,"title":["<i>\u200b<\/i>False-positive paracetamol levels in a patient with hyperbilirubinaemia: clinical perspectives"],"prefix":"10.1136","volume":"13","author":[{"given":"Joel","family":"James","sequence":"first","affiliation":[{"name":"Royal Preston Hospital, Preston, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Madelena","family":"Stauss","sequence":"additional","affiliation":[{"name":"Royal Preston Hospital, Preston, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Arvind","family":"Ponnusamy","sequence":"additional","affiliation":[{"name":"Royal Preston Hospital, Preston, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Martin","family":"Myers","sequence":"additional","affiliation":[{"name":"Royal Preston Hospital, Preston, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"239","published-online":{"date-parts":[[2020,6,30]]},"reference":[{"key":"2025082708372827000_13.6.e234702.1","doi-asserted-by":"publisher","DOI":"10.1177\/0885066615609271"},{"key":"2025082708372827000_13.6.e234702.2","doi-asserted-by":"crossref","first-page":"1389","DOI":"10.1038\/ajg.2017.98","article-title":"The natural history of severe acute liver injury","volume":"112","author":"Koch","year":"2017","journal-title":"Am J Gastroenterol"},{"key":"2025082708372827000_13.6.e234702.3","doi-asserted-by":"crossref","first-page":"S104","DOI":"10.1016\/j.jceh.2014.11.005","article-title":"Management in acute liver failure","volume":"5","author":"","year":"2015","journal-title":"J Clin Exp Hepatol"},{"key":"2025082708372827000_13.6.e234702.4","doi-asserted-by":"crossref","first-page":"38","DOI":"10.1016\/j.plabm.2015.12.003","article-title":"False positive acetaminophen concentrations in icteric serum","volume":"4","author":"de Jong","year":"2016","journal-title":"Pract Lab Med"},{"key":"2025082708372827000_13.6.e234702.5","doi-asserted-by":"publisher","DOI":"10.1373\/49.4.695"},{"key":"2025082708372827000_13.6.e234702.6","doi-asserted-by":"publisher","DOI":"10.1373\/clinchem.2010.144527"},{"key":"2025082708372827000_13.6.e234702.7","unstructured":"Kemp W , Roberts S . RACGP - FibroScan and transient elastography [Internet]. Racgp.org.au., 2013. Available: https:\/\/www.racgp.org.au\/afp\/2013\/july\/fibroscan\/ [Accessed 21 January 2019]."},{"key":"2025082708372827000_13.6.e234702.8","doi-asserted-by":"publisher","DOI":"10.1016\/j.cca.2008.01.018"},{"key":"2025082708372827000_13.6.e234702.9","doi-asserted-by":"publisher","DOI":"10.1081\/CLT-200057853"},{"key":"2025082708372827000_13.6.e234702.10","doi-asserted-by":"crossref","first-page":"287","DOI":"10.1016\/j.cca.2018.10.019","article-title":"Effect of hemolysis, icterus, and lipemia on three acetaminophen assays: potential medical consequences of false positive results","volume":"487","author":"Zhang","year":"2018","journal-title":"Clin Chim Acta"},{"key":"2025082708372827000_13.6.e234702.11","doi-asserted-by":"publisher","DOI":"10.1016\/S0140-6736(13)62062-0"},{"key":"2025082708372827000_13.6.e234702.12","doi-asserted-by":"crossref","first-page":"11","DOI":"10.1016\/j.eclinm.2019.04.005","article-title":"Safety and efficacy of the SNAP 12-hour acetylcysteine regimen for the treatment of paracetamol overdose","volume":"11","author":"Pettie","year":"2019","journal-title":"EClinicalMedicine"}],"container-title":["BMJ Case Reports"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/syndication.highwire.org\/content\/doi\/10.1136\/bcr-2020-234702","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,8,27]],"date-time":"2025-08-27T15:37:36Z","timestamp":1756309056000},"score":1,"resource":{"primary":{"URL":"https:\/\/casereports.bmj.com\/lookup\/doi\/10.1136\/bcr-2020-234702"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2020,6]]},"references-count":12,"journal-issue":{"issue":"6","published-online":{"date-parts":[[2020,6,30]]},"published-print":{"date-parts":[[2020,6]]}},"alternative-id":["10.1136\/bcr-2020-234702"],"URL":"https:\/\/doi.org\/10.1136\/bcr-2020-234702","relation":{},"ISSN":["1757-790X"],"issn-type":[{"type":"electronic","value":"1757-790X"}],"subject":[],"published":{"date-parts":[[2020,6]]}}}