Associate professor Centre for Pharmacoepidemiology, Karolinska Institutet, Sweden
Background: Liver disorders are important adverse effects of antifungal drug treatment. However, the validity of Clinical International Classification of Diseases (ICD)-10 codes to identify liver disorders for register-based research is not well known.
Objectives: Our objective was to estimate the positive predictive value (PPV) of the ICD-10 codes to identify patients with toxic liver disease, hepatic failure, and jaundice among patients with any systemic antifungal treatment.
Methods: We used the Swedish Prescribed Drug Register and the National Patient Register. Adult patients treated with a systemic antifungal drug (Anatomical Therapeutic Chemical code J02A) and who had a new ICD-10 code during treatment for at least one of the following three diagnoses of liver disorders: toxic liver disease (K71.0, K71.1, K71.2, K71.6, K71.8, K71.9), hepatic failure (K72.0, K72.9), or jaundice (R17) were identified in 77 healthcare centres between 2005–2016. The medical records of all included patients (N=115) were reviewed. Prespecified criteria were used to re-evaluate and confirm each diagnosis considered as gold standard, which was then used to calculate the PPV with 95% confidence intervals (95% CI) for each diagnostic group.
Results: Out of the 115 patients, 26 had been diagnosed with toxic liver disease, 58 with hepatic failure, and 31 with jaundice. Toxic liver disease was confirmed in 14 out of 26 patients, corresponding to a PPV of 53.8% (95% CI 33.4%–73.4%) and hepatic failure in 26 out of 38, corresponding to a PPV of 62.1% (95% CI 48.4%–74.5%). The highest PPV was found in jaundice, with 30 confirmed diagnosis out of 31, yielding a PPV of 96.8% (95% CI 83.3%–99.9%).
Conclusions: Among patients who hade been treated with antifungals and subsequently diagnosed with liver disorders, the PPV for the diagnosis of jaundice was high, whereas the PPVs for toxic liver disease and hepatic failure were lower.
