Barriers to effective sample management in viral load testing in Machakos County, Kenya: a convergent parallel mixed-method study.

Introduction: viral load (VL) monitoring is a critical component of HIV management, yet systemic and logistical barriers compromise the quality and reliability of VL sample management in many low- and middle-income countries. In Machakos County, Kenya, these challenges persist, contributing to a relatively low viral suppression rate of 81% and achievement of UNAIDS 95-95-95 strategy. This study determined barriers to effective VL sample management in Machakos County, Kenya, with a focus on equipment maintenance, human resource capacity, and supply chain performance across public and private facilities. Methods: a convergent parallel mixed-methods design was employed across 71 health facilities (61 public, 10 private) served by four VL hubs: Machakos Level 5, Matuu Level 4, Athi River Level 4, and Kangundo Level 4 hospitals. Quantitative data was collected from 205 healthcare workers using structured questionnaires. Descriptive statistics, Fisher's Exact Test, and Odds Ratios (OR) with 95% Confidence Intervals (CI) assessed associations between barriers and sample management outcomes. Qualitative data was obtained through 38 key informant interviews with clinicians from Comprehensive Care Clinics and Maternal and Child Health units (public n=32, private n=6). Transcripts were thematically analyzed using Braun and Clarke's framework, and a word cloud visualized common terms. Findings were triangulated for contextual depth. Ethical approval was obtained from the Kenya Medical Research Institute- Scientific Ethics Review Unit, with clearance from the Machakos County Department of Health. Informed consent was obtained and confidentiality were strictly maintained. Results: among the VL hubs assessed, 88.8% reported having a designated VL focal person, and 73.2% indicated that couriers had received some form of training. Despite these structural provisions, critical technical gaps persisted. Only 6.8% of facilities had calibrated centrifuges, 2.4% conducted preventive maintenance, and 2.4% calibrated their temperature monitoring devices-pointing to widespread neglect of equipment quality assurance protocols. Further, 58.5% of facilities reported incidents of sample freezing, often attributable to inconsistent cold chain practices. These deficits were not isolated but interrelated, collectively undermining the integrity of VL sample handling. Bivariate analysis revealed statistically significant associations between effective sample management and calibrated temperature devices (OR: 3.4; 95% CI: 1.6-7.0; p = 0.01), absence of sample freezing (OR: 2.8; 95% CI: 1.3-6.2; p= 0.03), and trained couriers (OR: 1.5; 95% CI: 0.9-2.7; p= 0.06), accentuating the importance of technical reliability alongside human resource readiness. The VL hubs with preventive maintenance showed significantly higher odds of effective sample management (OR: 4.5; 95% CI: 2.0-10.1; p< 0.001). Only 5.4% of facilities reported consistent availability of VL collection materials. Qualitative insights highlighted sporadic equipment servicing, recurrent stockouts, and poor coordination between facility-level operations and county logistics. Conclusion: persistent systemic barriers-such as inadequate equipment maintenance and fragmented supply chain management-undermine the effectiveness of VL sample management in Machakos County. Strengthening technical quality protocols, institutionalizing regular equipment maintenance, and enhancing supply chain coordination through the National AIDS and STI Control Program (NASCOP) and county health departments are critical to improving diagnostic reliability and advancing Kenya's HIV viral suppression targets.