title: A microcosting study of immunogenicity and tumour necrosis factor alpha inhibitor drug level tests for therapeutic drug monitoring in clinical practice.
abstract: OBJECTIVE
  To identify and quantify resource required and associated costs for implementing TNF-α inhibitor (TNFi) drug level and anti-drug antibody (ADAb) tests in UK rheumatology practice.
  
  
  METHODS
  A microcosting study, assuming the UK National Health Service perspective, identified the direct medical costs associated with providing TNFi drug level and ADAb testing in clinical practice. Resource use and costs per patient were identified via four stages: identification of a patient pathway with resource implications; estimation of the resources required; identification of the cost per unit of resource (2015 prices); and calculation of the total costs per patient. Univariate and multiway sensitivity analyses were performed using the variation in resource use and unit costs.
  
  
  RESULTS
  Total costs for TNFi drug level and concurrent ADAb testing, assessed using ELISAs on trough serum levels, were £152.52/patient (range: £147.68-159.24) if 40 patient samples were tested simultaneously. For the base-case analysis, the pre-testing phase incurred the highest costs, which included booking an additional appointment to acquire trough blood samples. The additional appointment was the key driver of costs per patient (67% of the total cost), and labour accounted for 10% and consumables 23% of the total costs. Performing ELISAs once per patient (rather than in duplicate) reduced the total costs to £133.78/patient.
  
  
  CONCLUSIONS
  This microcosting study is the first assessing the cost of TNFi drug level and ADAb testing. The results could be used in subsequent cost-effectiveness analyses of TNFi pharmacological tests to target treatments and inform future policy recommendations.
authors: Centre for Musculoskeletal Research.|Arthritis Research UK Centre for Epidemiology, Institute of Inflammation and Repair.
authors: Meghna
authors: M
authors: Jani
authors: Manchester Centre for Health Economics, Institute of Population Health, Manchester Academic Health Science Centre University of Manchester.|National Institute of Health Research Manchester Musculoskeletal Biomedical Research Unit, Central Manchester NHS Foundation Trust Manchester Academic Health Science Centre, Manchester.
authors: Sean
authors: S
authors: Gavan
authors: Centre for Musculoskeletal Research.|National Institute of Health Research Manchester Musculoskeletal Biomedical Research Unit, Central Manchester NHS Foundation Trust Manchester Academic Health Science Centre, Manchester.|Department of Rheumatology, Salford Royal NHS Foundation Trust, Salford.
authors: Hector
authors: H
authors: Chinoy
authors: Centre for Musculoskeletal Research.|Arthritis Research UK Centre for Epidemiology, Institute of Inflammation and Repair.|Department of Rheumatology, Salford Royal NHS Foundation Trust, Salford.
authors: William G
authors: WG
authors: Dixon
authors: Department of Rheumatology, Salford Royal NHS Foundation Trust, Salford.
authors: Beverley
authors: B
authors: Harrison
authors: Department of Immunology.
authors: Andrew
authors: A
authors: Moran
authors: Centre for Musculoskeletal Research.|National Institute of Health Research Manchester Musculoskeletal Biomedical Research Unit, Central Manchester NHS Foundation Trust Manchester Academic Health Science Centre, Manchester.|Kellgren Centre for Rheumatology, Manchester Royal Infirmary, Central Manchester University Hospitals NHS Foundation Trust, Manchester, UK.
authors: Anne
authors: A
authors: Barton
authors: Manchester Centre for Health Economics, Institute of Population Health, Manchester Academic Health Science Centre University of Manchester, katherine.payne@manchester.ac.uk.
authors: Katherine
authors: K
authors: Payne
mesh_terms: D000906:Antibodies / Q000378:metabolism; D003362:Cost-Benefit Analysis; D004180:Direct Service Costs; D016903:Drug Monitoring / Q000191:economics*; D004797:Enzyme-Linked Immunosorbent Assay / Q000191:economics; D006801:Humans; D012219:Rheumatology / Q000191:economics; D013222:State Medicine / Q000191:economics; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors* / Q000191:economics / Q000276:immunology; D006113:United Kingdom
chemical_list: D000906:Antibodies; D014409:Tumor Necrosis Factor-alpha
keywords: TNFi drug levels; health economics; immunogenicity; microcosting; opportunity costs