Screening blood donors for infection (note)
For educational purposes only. Check the current guidelines. Do not use this note to make clinical decisions.
Author: microregistrar
Updated: 6 November 2026
Scope: UK blood donation screening, with a comparison of living tissue, deceased tissue and stem-cell donation requirements.
This is an educational study note, written with microbiology and FRCPath revision in mind. It is not a clinical guideline, donor-eligibility tool or laboratory operating procedure. Use current JPAC guidance, national blood-service policy and the relevant tissue/transplant standards for clinical decisions.
Overview
Donor eligibility, laboratory screening and donation release are related but distinct decisions. Negative screening does not remove every infection risk, and a laboratory release provision does not automatically make a donor eligible under an individual blood service’s policy.
The main laboratory source is the JPAC Red Book, section 9.2: Microbiology screening, updated 19 August 2026. It now provides separate tables for blood, living tissue, deceased tissue and cells/cord blood. Assay-performance requirements are in section 9.3: Specific screening targets, updated 23 May 2025. Both were checked for this revision.
1. What do the screening categories mean?
| Category | Meaning |
|---|---|
| Mandatory | A regulatory requirement, or a test deemed necessary to meet regulatory requirements for donor suitability and donor/recipient protection. |
| Discretionary | Must be performed for certain donors/donations when indicated by medical, social, travel or donation history. It does not mean the test can simply be omitted when the indication is present. |
| Recommended | Recommended by an advisory committee or professional body, but not a regulatory requirement. |
| Optional | Performed at the discretion of the organisation or establishment; this also includes discretionary repetition of an otherwise mandatory test. |
When additional screening is required, its results form part of the donation-release criteria. Services may exceed the specified minimum standards, for example by testing individually instead of in pools. Source: JPAC 9.2
2. Blood donation screening
The table below follows the current terminology in JPAC Table 9.1. “Pooled” describes the permitted screening format; individual testing or smaller pools may be used.
| Infectious agent | Marker | Requirement | Format |
|---|---|---|---|
| HBV | HBsAg | Mandatory | Individual |
| HBV | HBV DNA | Recommended | Pooled |
| HBV | Anti-HBc | Discretionary: defined minimum screening schedule applies | Individual |
| HCV | Anti-HCV | Mandatory | Individual |
| HCV | HCV RNA | Mandatory | Pooled |
| HEV | HEV RNA | Mandatory | Pooled |
| HIV | HIV-1/2 antigen/antibody | Mandatory | Individual |
| HIV | HIV RNA | Mandatory in Scotland; recommended elsewhere | Pooled |
| HTLV-I/II | Anti-HTLV-I/II | Discretionary: defined minimum screening schedule applies | Individual |
| Syphilis | Anti-treponemal antibodies | Mandatory | Individual |
| CMV | Anti-HCMV | Optional | Individual |
| Malaria | Anti-P. falciparum/vivax | Discretionary | Individual |
| Trypanosoma cruzi | Anti-T. cruzi | Discretionary | Individual |
| West Nile virus | WNV RNA | Discretionary | Pooled |
| HAV | HAV RNA | Optional in the blood table; product-specific requirement for plasma-derived medicines | Pooled |
| Human parvovirus B19 | B19 DNA | Optional in the blood table; product-specific requirement for plasma-derived medicines | Pooled |
Source: JPAC 9.2, Table 9.1 and notes.
HIV and HBV molecular screening
Although HIV RNA and HBV DNA are not independently mandatory for blood donations in most of the UK, they are included in molecular screening because commercial systems are multiplex assays. HIV RNA is mandatory in Scotland. HIV assays should cover HIV-1 groups M, N and O; section 9.2 recommends dual-target HIV-1 NAT and assays detecting HIV-2. Section 9.3 separately requires two HIV genomic targets for HIV RNA screening.
Anti-HBc: who is screened?
As a minimum, all blood donors are screened:
- At their first donation, or their first donation after introduction of anti-HBc screening.
- Again after a donation lapse of more than two years.
- Again if a new HBV risk is identified.
Anti-HBc screening is therefore neither an unspecified optional extra nor necessarily a test repeated at every blood donation. In contrast, anti-HBc is mandatory at each tissue/stem-cell donation. Sources: JPAC 9.2 and 9.3.8.
Anti-HTLV: who is screened?
As a minimum, screen all blood donors at their first donation or first donation after introduction of anti-HTLV screening. Screening is also required for donations intended for non-leucodepleted products and is repeated if a donor has a new HTLV risk. The current table classifies this as discretionary screening with a specified minimum schedule, rather than universal testing at every donation.
CMV
Anti-HCMV is optional in the blood-donation table. Ideally both IgG and IgM are tested, but IgG alone is considered sufficient. Requirements for particular recipients/components must be checked separately.
HAV and B19: donation screening versus plasma-pool requirements
The Table 9.1 footnote identifies requirements for plasma collected for plasma-derived medicinal products. Section 9.3.17 explains that testing of the first homogeneous manufacturing plasma pool depends on the product, and that there is no universal mandatory requirement to test every individual donation for HAV or B19. Services may screen minipools to reduce the risk of discarding larger pools.
Do not describe HAV/B19 NAT as universal routine screening of all transfusion components. Source: JPAC 9.3.17
3. Anti-HBc-positive donations: release is service-dependent
Blood donations
Current Red Book sections 9.2.5 and 9.4.1 allow acceptance of anti-HBc-positive blood donations with anti-HBs greater than 100 IU/L, at the discretion of individual blood services. If that pathway is used:
- The donor must remain HBV DNA negative by individual-donation NAT at every subsequent donation.
- Anti-HBs must be retested at least every two years and remain greater than 100 IU/L.
- Other mandatory screening and donor-eligibility requirements still apply.
100 IU/L is equivalent to 100 mIU/mL. The threshold in the cited blood pathway is greater than 100, not merely a detectable anti-HBs result.
However, the uploaded Whole Blood and Components Donor Selection Guidelines state, under the hepatitis B entry, that donors identified as anti-HBc positive by Blood Transfusion Service testing must not donate. Thus the Red Book’s permitted service-dependent pathway must not be presented as routine acceptance in every UK service. Local implementation must be established; do not use either document in isolation to override the service’s policy.
Sources: JPAC 9.2.5, 9.4.1, and uploaded WB-DSG, hepatitis B entry, pages 131–134.
Tissue and cell donations
Anti-HBc-reactive tissue/cell donations may be considered for release when HBsAg is negative and sensitive individual HBV DNA testing is negative. The specified HBV DNA assay performance for this pathway is a 95% limit of detection of 20 IU/mL or below. Anti-HBs above 100 IU/L is not required for this tissue/cell pathway.
This specific release requirement must not be confused with section 9.3.12’s statement that there is no general UK numerical minimum sensitivity requirement for HBV DNA screening. Sources: JPAC 9.2.5 and 9.4.1
4. Tissue and cell donations: separate pathways
Core screening comparison
| Marker | Living tissue | Deceased tissue | HPC, therapeutic cells, cord blood and human embryonic stem-cell donations |
|---|---|---|---|
| HBsAg | Mandatory, individual | Mandatory, individual | Mandatory, individual |
| Anti-HBc | Mandatory, individual | Mandatory, individual | Mandatory, individual |
| HBV DNA | Recommended, individual | Mandatory, individual | Recommended, pooled permitted; individual testing for anti-HBc-positive release |
| Anti-HCV | Mandatory, individual | Mandatory, individual | Mandatory, individual |
| HCV RNA | Recommended, individual | Mandatory, individual | Recommended, pooled permitted |
| HIV-1/2 antigen/antibody | Mandatory, individual | Mandatory, individual | Mandatory, individual |
| HIV RNA | Recommended, individual | Mandatory, individual | Recommended, pooled permitted |
| Anti-treponemal antibodies | Mandatory, individual | Mandatory, individual | Mandatory, individual |
| Anti-HTLV-I/II | Discretionary, individual; see risk criteria below | Discretionary, individual; see risk criteria below | Discretionary, individual; see risk criteria below |
| HEV RNA | Optional, pooled permitted | Optional, normally individual; limited ante-mortem exception | Discretionary, pooled permitted |
| Malaria antibodies | Discretionary, individual | Discretionary, individual | Discretionary, individual |
| Malaria DNA | Optional, individual; relevant to antibody-positive pathways | Optional, individual; relevant to antibody-positive pathways | Optional, individual; relevant to antibody-positive pathways |
| Anti-T. cruzi | Discretionary, individual | Discretionary, individual | Discretionary, individual |
| WNV RNA | Discretionary, pooled permitted | Discretionary, normally individual; limited ante-mortem exception | Discretionary, pooled permitted |
Source: JPAC 9.2, Tables 9.2–9.4. HCV antigen and/or combined HCV antigen/antibody testing is additionally optional in the living and deceased tissue tables.
Living tissue: NAT or quarantine
HIV/HBV/HCV NAT is not mandatory for all living tissue donations. If NAT is not performed on the donation sample, tissue must be quarantined for at least 180 days and a further sample taken for serology before release. If quarantine is not used, the recommendation for individual HBV DNA testing and the multiplex nature of commercial assays mean testing is by individual-donation NAT for HBV, HCV and HIV.
Deceased tissue
HBV DNA, HCV RNA and HIV RNA are mandatory individual tests. HEV and WNV testing is normally individual. Samples taken ante-mortem before circulatory arrest may be pooled for HEV RNA and WNV RNA within the specified validated maxima.
Stem cells, therapeutic cells and cord blood
HBV/HCV/HIV NAT is recommended, rather than mandatory in Table 9.4, and replaces the need for quarantine and follow-up serological screening. Apply product-specific timing, registry, transplant and recipient requirements; the table is not permission to omit a test required by the treating programme.
Anti-EBV and anti-HCMV are listed as recommended/optional, with details directed to Annex 7. CMV IgG alone is considered sufficient, although testing IgG and IgM is ideal.
Toxoplasma gondii IgG and IgM screening is recommended in allogeneic HPC and therapeutic-cell donation. IgM-positive donors should be avoided, and isolated IgM reactivity should be confirmed because of specificity limitations. The current Table 9.4 displays a pooled format for toxoplasma antibodies; section 9.2.5 and Annex 7 provide the clinical context. Do not infer a general permission to pool transplant serology from the NAT pool-size rules.
HTLV: risk-based requirement, universal testing in practice
In the tissue/cell tables, anti-HTLV is discretionary. It is required for donors who live in or originate from high-prevalence areas, whose sexual partners originate from such areas, or whose parents originate from such areas. JPAC states that, in practice, all tissue and cell donations are tested.
Do not retain the older blanket description “mandatory except avascular tissue” as the current table’s classification.
Deceased neonatal and infant tissue donors
- Full maternal microbiology screening is always required.
- For stillbirths and neonates up to 28 days after birth, microbiology screening of the neonate is not required.
- Beyond 28 days after birth, full screening of an infant sample is also required.
Source for this section: JPAC 9.2.
5. NAT pooling and assay sensitivity
Current maximum validated NAT pool sizes
| Target | Maximum number of donations |
|---|---|
| WNV | 16 |
| HBV, HCV, HEV and HIV | 24 |
| HAV and B19 | 96 |
These maxima do not override requirements for individual testing. The actual pool size requires risk assessment considering assay sensitivity, endemicity, residual risk and any fractionator requirements. The 95% limit of detection is the lowest concentration detected in 95% of positive samples. Source: JPAC 9.2
Minimum sensitivity and quality-control requirements
| Target | Current JPAC specification |
|---|---|
| HBsAg | Minimum screening sensitivity 0.2 IU/mL. The additional QC must have a unitage of 0.2 IU/mL or less. |
| HIV serology | Positive result during evaluation/validation/verification with QC calibrated to the WHO International Reference Reagent. A combined p24 antigen/HIV-1/2/O antibody assay is recommended. There is no separate requirement to demonstrate individual anti-HIV-2 or p24 reactivity in this QC specification. |
| Anti-HCV, anti-HTLV-I/II, syphilis antibody, anti-T. cruzi, anti-HBc, anti-HCMV and anti-HBs | Positive result with QC calibrated to the relevant WHO International Standard; the applicable validated alternative is used where standardisation/material is unavailable. |
| Malaria antibodies | At least anti-P. falciparum/vivax; positive result with QC calibrated to the WHO International Reference Reagent, or a validated alternative if unavailable. |
| HCV RNA | Minimum sensitivity 5,000 IU/mL in an individual donation. A specific internal control is required for each sample. |
| HBV DNA | No general numerical UK minimum sensitivity specified in 9.3.12. A specific internal control is required for each sample. A separate ≤20 IU/mL 95% LoD applies to the anti-HBc-positive tissue/cell release pathway. |
| HIV RNA | No general numerical UK minimum sensitivity specified. A specific internal control is required for each sample. The assay must use two separate genomic targets to reduce the risk from sequence variation. |
| HEV RNA and WNV RNA | No general numerical UK minimum sensitivity specified. A specific internal control is required for each sample. |
| HAV RNA and B19 DNA | No general numerical UK minimum sensitivity specified. Minipool testing must meet the manufacturing-pool objectives described below. |
Source: JPAC 9.3. “No general numerical minimum” does not mean absence of validation, sensitivity, pooling or product-specific requirements.
Serology QC
For the serological targets described in section 9.3, an additional QC must be included at least once in each test series, alongside the assay manufacturer’s controls. It must be manufactured by a different manufacturer from the assay manufacturer; where available, it should be CE- or UKCA-marked. The required controls must meet their acceptance criteria before the series is accepted. International Standards/Reference Reagents themselves do not need CE or UKCA marking.
Molecular QC
Each sample requires a specific internal control. Manufacturer controls and any additional QC used must satisfy the defined acceptance criteria. If an additional QC is run with each series, it should be independently manufactured and CE/UKCA-marked where available. Do not automatically transfer the mandatory additional-serology-QC wording to every NAT assay.
Plasma for fractionation
Where minipool screening is used, it must ensure:
- B19 DNA below 10⁴ IU/mL in the homogeneous manufacturing plasma pool.
- A negative HAV NAT result in the homogeneous manufacturing plasma pool.
These are manufacturing-pool objectives, not the universal sensitivity threshold for every individual blood donation. Source: JPAC 9.3.17
6. Reactive screening results and confirmation
Terminology
- Initial reactive: the first result exceeds the manufacturer’s cut-off.
- Repeat reactive: reactivity on at least two occasions in the defined screening pathway.
- Confirmed positive: reference testing meets predefined criteria for current or past infection.
- Non-specific reactivity: reference investigation concludes that screening reactivity does not reflect infection.
A reactive screening result is not by itself a diagnosis.
Blood serology
For a first-time initially reactive result, repeat in duplicate using the same assay. The donation may be considered for release only if both repeats are non-reactive and all other release requirements are met. Reactivity in either repeat makes the donation unsuitable, subject to the specific anti-HBc release exception.
A previously investigated donor with established non-specific reactivity may follow a validated alternative-screening-assay pathway. The alternative assay must have at least equivalent sensitivity. Reference-laboratory investigation and donor-record flags remain essential.
Tissue and cell serology
Repeat initially reactive samples in duplicate using the same assay or a specifically evaluated alternative of at least equal sensitivity, ideally based on different antigens, antibodies or principles. Some repeat-reactive tissue/cell donations may be usable following confirmation and a defined clinical risk assessment; do not apply routine blood-donation rules without considering the tissue/cell pathway.
NAT
Resolve initially reactive pools to the individual reactive donation(s). Non-reactive donations may be considered for release if all other requirements are met. Individual reactive blood donations are unsuitable for transfusion. Stem-cell products from known infected individuals may have exceptional clinical pathways.
Confirmatory testing and donor follow-up
Screen reactivity in the specified mandatory/additional tests requires confirmation at a designated reference laboratory, except anti-HCMV. Appropriate donor advice and referral follow confirmed positive results. Specific HBsAg neutralisation may be required to avoid misclassifying low-level HBsAg reactivity as non-specific.
Sources: JPAC 9.2.3–9.2.5 and 9.4.
Temporary exclusion and reinstatement
| Confirmed marker | Red Book reinstatement pathway |
|---|---|
| HEV, HAV or WNV RNA | Normally six months from the index RNA-positive donation; reinstatement without further testing after that interval. |
| HEV: earlier reassessment | Earlier reinstatement may be possible with individual HEV RNA negative and HEV IgG ≥1 IU/mL using the specified PEI standard. IgM may still be present. |
| B19 DNA | Four weeks from the index DNA-positive donation; reinstatement without further testing after that interval. |
These are laboratory-screening reinstatement pathways, not a substitute for the relevant disease-specific donor-selection criteria and clinical recovery assessment. Confirmed positive donors are otherwise not normally reinstated, including after successful treatment where serological reactivity persists. Source: JPAC 9.4
7. Residual risk
Residual risk is the estimated risk that a potentially infectious window-period donation escapes testing and may enter the blood supply. It is not the probability that a recipient acquires infection.
The September 2025 JPAC statement provides the verified figures below for UK whole-blood donations during 2022–2024. Molecular testing in the model used pools of 24 donations.
| Virus | Screening assumed | Assumed window period | Undetected potentially infectious window-period donations per million donations, all donors |
|---|---|---|---|
| HBV | HBsAg and HBV DNA NAT | 30 days | 1.09; 95% CI 0.63–3.35 |
| HCV | Anti-HCV and HCV RNA NAT | 4 days | <0.01 |
| HIV | Combined antigen/antibody and HIV NAT | 9 days | 0.10; confidence-interval discrepancy noted below |
The source’s HIV narrative gives a 95% CI of 0.04–0.28, while Table 1 gives 0.04–0.17 for all donors. The point estimate is consistent; an unqualified confidence interval should not be copied without resolving the discrepancy.
Interpretation
- HBV has the highest modelled window-period residual risk among these three viruses.
- The HBV estimate covers acute infections only; it excludes occult HBV. Anti-HBc screening, rolled out across the UK in 2022, addresses an additional risk.
- No HCV seroconversions were observed in 2022–2024. The estimate is <0.01 per million, not zero.
- These window periods are assumptions for the modelled screening strategies, not universal diagnostic windows for clinical testing.
- The estimates exclude convalescent plasma and plasma for medicines, which follow different testing/processing pathways.
- HEV is not routinely included in this model because of uncertainty about its window period and fluctuating incidence. Its absence does not imply negligible risk; separate HEV estimates are not directly interchangeable with this table.
Source: JPAC residual-risk position statement, September 2025. These are the latest figures verified for this revision; check for a replacement before quoting them as current in future.
8. Travel risks and suspected transfusion-transmitted infection
Travel-related malaria, WNV and Chagas risks require the relevant donor-selection guidance and current geographical risk assessment. A negative test does not override a required deferral unless the guideline explicitly permits that testing pathway. Use the guidance specific to blood, tissue or cells.
Suspected transfusion-transmitted infection should be reported promptly through the treating hospital’s transfusion team and supplying blood service for investigation under the applicable haemovigilance procedures. Do not label an infection confirmed transfusion-transmitted solely because it developed after transfusion. Laboratory screening and donor investigation must be connected to the clinical case.
For investigation procedures, see JPAC Red Book, Chapter 10.
9. Examination-focused summary
| Topic | Key point |
|---|---|
| Mandatory blood screening | HBsAg, anti-HCV and HCV RNA, HIV antigen/antibody, HEV RNA and treponemal antibodies; HIV RNA is also mandatory in Scotland. |
| Anti-HBc and anti-HTLV in blood | Discretionary categories with explicit minimum screening schedules, not necessarily testing at every donation. |
| Anti-HBc in tissues/cells | Mandatory at each donation. |
| Deceased tissue | Individual HBV DNA, HCV RNA and HIV RNA are mandatory. |
| Living tissue | Individual HIV/HBV/HCV NAT is recommended; if not performed, the ≥180-day quarantine and repeat-serology pathway applies. |
| Stem-cell NAT | Recommended in the general screening table; apply specific transplant/registry requirements. |
| HEV | Mandatory for blood; optional for living/deceased tissue; discretionary for the cell/cord-blood table. |
| HTLV in tissue/cells | Risk-based requirement, but JPAC states all are tested in practice. |
| Anti-HBc-positive blood | Service-dependent Red Book exception; never assume universal eligibility. |
| HBsAg assay sensitivity | 0.2 IU/mL. |
| HCV NAT sensitivity | 5,000 IU/mL in an individual donation. |
| HIV NAT | Two genomic targets required by section 9.3. |
| Anti-HBc-positive tissue/cell release | HBsAg negative and sensitive individual HBV NAT negative; HBV NAT 95% LoD ≤20 IU/mL. |
| Residual risk | Missed potentially infectious donations, not observed transmission probability. |
Source currency and editorial note
This article replaces the previous draft. It uses the live JPAC screening tables updated 19 August 2026, rather than the older March 2025 PDF. It also incorporates the current accessible section 9.3 assay specifications and section 9.4 reinstatement provisions. The previous combined tissue/stem-cell table and the statement that assay specifications could not be verified have been removed.
The uploaded WB-DSG is used to flag the anti-HBc donor-eligibility difference rather than to erase the Red Book’s explicit service-dependent exception. The discrepancy requires service-specific interpretation, not a claim that one route applies universally.
The residual-risk figures remain those in the verified September 2025 statement. Guidance is continuously updated; the review date is not a guarantee that every local service has implemented an identical policy.