Patient-Led Remote Intracapillary Pharmacokinetic Sampling (Fingerpricks): Validation and Acceptability for Home Therapeutic Drug Monitoring in Patients with Ibd in the COVID-19 Pandemic

Abstract

Background: During the first wave of the coronavirus (COVID-19) pandemic, restrictive public health measures including prolonged shielding, were recommended by the United Kingdom government for many patients with immune-mediated inflammatory disorders treated with immunosuppressive and biologic drugs. Low-volume intracapillary blood sampling can be undertaken by patients at home and returned by post and may ensure access to therapeutic drug monitoring (TDM) for all patients irrespective of shielding status.Methods: We undertook a cross-sectional blood sampling methods comparison study to assess the clinical validity and acceptability to patients of low volume intracapillary testing for serum TDM enzyme-linked immunosorbent assays (ELISA) compared to conventional venepuncture. Sample types were compared using linear regression and fit-for-purpose equivalence was defined using total allowable error (TEa) rates derived using interassay coefficient of variations from routine clinical practice. Acceptability was assessed using a purpose-designed questionnaire.Findings: The median (IQR) volume of serum obtained using intracapillary sampling was 195µL (130-210). We showed drug level equivalence (slope [95% CI]: TEa vs observed mean % difference) between intracapillary sampling and conventional venepuncture for adalimumab (1·02 [0·90-1·14]: 11·7% vs 2·1%), infliximab (1·08 [0·98-1·18]: 18·3% vs 1·2%), vedolizumab (0·91 [0·85-0·96]: 17·6% vs 4·1%), and ustekinumab (0·92 [0·90-0·94]: 19·4% vs 3·3%). Anti-drug antibody equivalence was observed for anti-adalimumab (0·96 [0·95-0·98]: 24·5% vs 2·1%) and anti-infliximab (0·89 [0·81-0·97]: 17·3% vs 1·3%) antibody levels. Most patients reported that intracapillary testing was easy, convenient, and that they preferred it to conventional venepuncture.Interpretation: Low-volume intracapillary blood sampling was equivalent to conventional venepuncture for the measurement of biologic drug and anti-drug antibodies. Patients preferred intra-capillary testing to conventional venepuncture. Irrespective of future COVID-19 surges, patient-led intracapillary blood sampling is likely to become a key adjunct to telemedicine in patients with immune-mediated inflammatory diseases.Funding: Novo Nordisk Foundation. NIHR Exeter Clinical Research Facility. The Academic Department of Blood Sciences, RDE NHS Trust.Declaration of Interests: All authors have completed the ICMJE Form for Disclosure of Potential Conflicts of Interest and declare: D.C received honoraria from Ferring and Pfizer outside of this work; N.A.K has consulted for Falk and received honoraria from Falk, Allergan, Pharmacosmos and Takeda for unrelated topics and is a deputy editor of Alimentary Pharmacology & Therapeutics Journal; T.A has received unrestricted research grants, advisory board fees, speaker honorariums and support to attend international meetings from AbbVie, Merck, Janssen, Takeda, Ferring, Tillotts, Ferring, Pfizer, NAPP, Celltrion, Hospira for unrelated topics, no financial relationships with any organizations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work. R.N, B.H, E.J, S.H, C.R, V.C, K.P, J.R.G and T.J.M have no conflicts of interest to declare.Ethics Approval Statement: The sponsor was the Royal Devon and Exeter NHS Foundation Trust and the South West Research Ethics Committee approved the study (IRAS Reference Number: 286396; July 2020).