Background:
Dried Blood Spot (DBS) testing is widely used for blood borne virus screening within substance use services. In July 2024, Inclusion NHS community services noticed a disproportionate number of samples returning hepatitis B and HIV positive results (n= 43/164). Upon investigation, it was identified that supply chain disruptions had led to the temporary use of alternative DBS cards from the same supplier. This raised concerns about diagnostic reliability, necessitating a revised model of care to mitigate inaccuracies and maintain multi-level trust in DBS diagnostics.
Description of model of care:
A structured response was implemented to address identified inaccuracies, incorporating 1)
Rapid identification and response: routine quality control and external reports flagged increased false reactivity rates, prompting immediate investigation; 2) Adaptation of laboratory procedures: the alternative DBS cards were found to absorb diluents differently, requiring modification of sample preparation; 3) Enhanced confirmatory testing: all low-positive reactive samples underwent immediate reflex confirmatory testing using venous or capillary serum samples to validate results before clinical decision-making; 4) Stakeholder engagement: regular communication with Inclusion ensured transparency, reduced unnecessary patient concern, and facilitated rapid adjustments in sample handling; and 5) Return to validated testing materials: fast-tracking the supply of custom-validated DBS cards restored accurate diagnostic capabilities, resolving the issue.
Effectiveness:
Following the intervention, false-reactive rates returned to baseline. Confirmatory testing ensured no patients were misdiagnosed preserving clinician confidence in DBS testing. This incident and response reinforced the importance of ongoing validation in diagnostic supply chains.
Conclusion and Next Steps:
This model of care highlights the necessity of robust quality assurance in DBS testing, rapid adaptability to supply chain changes, and clear communication strategies to mitigate diagnostic errors. Future steps include expanded validation studies for alternative DBS cards and exploring the feasibility of capillary blood sampling as a backup strategy to ensure diagnostic integrity. |