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PA21.1-6 | Transfusion-Transmitted Infections — Part 3

Multi-Layer Prevention Strategy

A defence-in-depth blood safety diagram showing donor selection, serological screening, nucleic acid testing, and pathogen reduction technology progressively reducing transfusion-transmitted infection risk. — **Panel A:** Defence-in-depth overview showing blood donation passing through four protective shields: donor selection and deferral, serological screening, NAT, and pathogen reduction technology before safe transfusion.. **Panel B:** Donor selection and deferral showing voluntary non-remunerated donor selection, donor questionnaire, permanent deferral examples, and temporary deferral examples.. **Panel C:** Serological screening showing mandatory screening tests for HIV, HBV, HCV, syphilis, and malaria, with reactive unit quarantine, confirmatory testing, donor notification, and permanent deferral.. **Panel D:** Nucleic acid testing showing NAT detection of viral nucleic acid, reduced window period, and particular benefit for HCV and HIV detection.. **Panel E:** Pathogen reduction technology showing psoralen plus UV-A and solvent-detergent methods applied to platelets and plasma to reduce viruses, bacteria, and parasites..

Blood safety is not a single test — it is a defence-in-depth system. Each layer reduces but does not eliminate risk; the combination achieves very low residual rates.

Layer 1 — Donor selection and deferral:
The first line is selecting low-risk donors:
- Voluntary non-remunerated donors (VNRD) have lower TTI prevalence than replacement/paid donors.
- Permanent deferral: HIV-positive donors, HBsAg-positive, HCV-positive, vCJD-risk exposure.
- Temporary deferral: Febrile illness in past 28 days, recent dental procedure, tattooing/piercing in past 6 months, pregnancy, recent travel to malaria-endemic area.
- A detailed donor questionnaire (health history) is integral to this layer.

Layer 2 — Serological screening:
The five mandatory NACO tests plus any locally required additions. Reactive units are quarantined, confirmatory testing is performed, and confirmed-positive donors are permanently deferred and notified.

Layer 3 — Nucleic acid testing (NAT):
Reduces the window period. Increasingly mandatory across Indian blood banks. Particularly cost-effective for HCV (high window-period reduction) and HIV.

Layer 4 — Pathogen reduction technology (PRT):
Pathogen reduction uses photochemical (psoralen + UV-A) or solvent-detergent methods to inactivate a broad spectrum of enveloped viruses, non-enveloped viruses, bacteria, and parasites directly in the blood component. Currently available for platelets (Intercept, Mirasol systems) and plasma; red cell pathogen reduction is in development. Not yet universally available in India but used in some reference centres.

Layer 5 — Appropriate use and clinical governance:
The safest transfusion is the one not given. Restrictive transfusion triggers (e.g., Hb <7 g/dL in stable adult vs <8 g/dL in cardiac patients) reduce exposure. Haemovigilance — systematic reporting of transfusion reactions and adverse events including suspected TTIs — enables learning from incidents and drives policy. The look-back programme traces all recipients from a donor subsequently found infected to offer testing and counselling.

SELF-CHECK

Pathogen reduction technology using psoralen and UV-A light is CURRENTLY applicable to which blood component in clinical practice?

A. Red cell concentrates

B. Granulocyte concentrates

C. Cryoprecipitate

D. Platelets and fresh frozen plasma

Reveal Answer

Answer: D. Platelets and fresh frozen plasma

Pathogen reduction using the psoralen + UV-A (Intercept) or riboflavin + UV (Mirasol) systems is currently clinically validated and in use for platelets and fresh frozen plasma. Red cell pathogen reduction technology is still in advanced development phases but not yet widely in clinical use. Granulocytes are rarely transfused and have no approved PRT system. Cryoprecipitate is a plasma derivative but does not have a widely approved PRT protocol.

CLINICAL PEARL

Bacterial contamination of platelets > viral TTI as a cause of transfusion death. Commit this hierarchy: bacterial contamination of platelets > HIV/HBV/HCV > malaria (in terms of transfusion-related mortality in India). When a patient spikes a fever during a platelet transfusion — stop the transfusion, take cultures from the bag and patient, and treat empirically for Gram-positive sepsis while awaiting results. Do not restart the transfusion even if the patient improves — a gram-positive endotoxin load may be contributing to transient clinical improvement.