Web-based Application for the Population Pharmacokinetic Service (WAPPS)'s impact on dosage selection: a single paediatric centre experience

Abstract Background Current treatment for severe haemophilia includes prophylactic factor replacement to prevent bleeding. Coagulation factor products have significant inter-patient variability in pharmacokinetic (PK) parameters. Optimal management requires tailoring prophylaxis to individual PK parameters. Web-based Application for the Population Pharmacokinetic Service (WAPPS) is a tool that estimates individual PK values using a population approach. Despite its growing use to help guide dosing selection, few studies have investigated its clinical impact. Aim To investigate any change in prophylaxis regimen and hours per week where factor level is under 1%, pre- and post-PK testing using WAPPS, for paediatric patients with severe haemophilia. Methods A retrospective chart review was conducted for all paediatric patients with severe haemophilia receiving care between April 2013 and July 2018 at McMaster Children's Hospital who have used WAPPS. Data extracted included: patient demographics, PK data generated by WAPPS, prophylaxis regimen pre- and post-PK testing, and reason for regimen change. The number of hours per week where factor level was under 1% pre- and post-PK testing was calculated using WAPPS. Results Thirty-one patients were included; 42% (n=13) changed their prophylaxis regimen after PK testing. After using PK data to personalise prophylaxis recommendations, there was a decrease in the number of hours per week where factor level is under 1% (from an average of 13.1 hours/week to 11.8 hours/week), though not statistically significant (p=0.16). Conclusion PK data generated by WAPPS has direct impact by informing changes to prophylaxis recommendations. This individualised approach promotes patient-centred care and patient engagement without increasing the time spent with factor levels below 1%. It also confirms and validates clinical practice.