title: Prediction of liver disease in patients whose liver function tests have been checked in primary care: model development and validation using population-based observational cohorts.
abstract: OBJECTIVE
  To derive and validate a clinical prediction model to estimate the risk of liver disease diagnosis following liver function tests (LFTs) and to convert the model to a simplified scoring tool for use in primary care.
  
  
  METHODS
  Population-based observational cohort study of patients in Tayside Scotland identified as having their LFTs performed in primary care and followed for 2 years. Biochemistry data were linked to secondary care, prescriptions and mortality data to ascertain baseline characteristics of the derivation cohort. A separate validation cohort was obtained from 19 general practices across the rest of Scotland to externally validate the final model.
  
  
  METHODS
  Primary care, Tayside, Scotland.
  
  
  METHODS
  Derivation cohort: LFT results from 310 511 patients. After exclusions (including: patients under 16 years, patients having initial LFTs measured in secondary care, bilirubin >35 μmol/L, liver complications within 6 weeks and history of a liver condition), the derivation cohort contained 95 977 patients with no clinically apparent liver condition. Validation cohort: after exclusions, this cohort contained 11 653 patients.
  
  
  METHODS
  Diagnosis of a liver condition within 2 years.
  
  
  RESULTS
  From the derivation cohort (n=95 977), 481 (0.5%) were diagnosed with a liver disease. The model showed good discrimination (C-statistic=0.78). Given the low prevalence of liver disease, the negative predictive values were high. Positive predictive values were low but rose to 20-30% for high-risk patients.
  
  
  CONCLUSIONS
  This study successfully developed and validated a clinical prediction model and subsequent scoring tool, the Algorithm for Liver Function Investigations (ALFI), which can predict liver disease risk in patients with no clinically obvious liver disease who had their initial LFTs taken in primary care. ALFI can help general practitioners focus referral on a small subset of patients with higher predicted risk while continuing to address modifiable liver disease risk factors in those at lower risk.
authors.affiliation: Medical Statistics Team, Division of Applied Health Sciences, College of Life Sciences and Medicine, University of Aberdeen, Aberdeen, UK.
authors.forename: David J
authors.initials: DJ
authors.lastname: McLernon
authors.affiliation: Dundee Epidemiology and Biostatistics Unit, Division of Population Health Sciences, Medical Research Institute, University of Dundee, Dundee, UK.
authors.forename: Peter T
authors.initials: PT
authors.lastname: Donnan
authors.affiliation: Department of Community and Family Medicine, University of Toronto, Toronto, Canada.
authors.forename: Frank M
authors.initials: FM
authors.lastname: Sullivan
authors.affiliation: Academic Unit of Primary Care and Population Sciences, Faculty of Medicine, University of Southampton, Southampton, UK.
authors.forename: Paul
authors.initials: P
authors.lastname: Roderick
authors.affiliation: Centre for Hepatology, Division of Medicine and ULCH-UCL NIHR Biomedical Research Centre, University College London, London, UK.
authors.forename: William M
authors.initials: WM
authors.lastname: Rosenberg
authors.affiliation: Department of Gastroenterology, Nottingham University Hospitals NHS Trust and Biomedical Research Unit, Nottingham, UK.
authors.forename: Steve D
authors.initials: SD
authors.lastname: Ryder
authors.affiliation: Medical Research Institute, University of Dundee, Dundee, UK.
authors.forename: John F
authors.initials: JF
authors.lastname: Dillon
mesh_terms: D000328:Adult; D000368:Aged; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008107:Liver Diseases / Q000175:diagnosis* / Q000453:epidemiology; D008111:Liver Function Tests; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D011237:Predictive Value of Tests; D011320:Primary Health Care; D018570:Risk Assessment; D012606:Scotland
keywords: EPIDEMIOLOGY; PRIMARY CARE