Discordant rapid HIV tests in pregnancy after a cold-chain breach
A 28-year-old pregnant woman attends an antenatal clinic at 14 weeks gestation. A rapid HIV test using whole blood is reactive. The clinic has a second rapid test of a different brand and a third tie-breaker test, but the nurse is unsure of the national algorithm. The woman is asymptomatic and has no record of previous HIV testing. She is frightened and asks whether she definitely has HIV and whether her baby will be infected. Her partner is not present. The clinic's register shows that the rapid test kit was stored in a room where the temperature reached 38°C for two days last week. The clinic is in a rural district. What should the laboratory adviser recommend for confirmation, and how should the result be communicated?
1. Describe how the three rapid tests should be used in the national serial algorithm and what interpretation follows if test 1 is reactive, test 2 is non-reactive and test 3 is reactive.
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Algorithm. In a serial national algorithm, a reactive first test is not a diagnosis. The sample should be tested with the second test; if that is non-reactive, the third tie-breaker is used. A reactive tie-breaker after a discordant second test is interpreted as HIV-positive under the national algorithm, but the final report must follow the national interpretation table exactly.
Storage problem. The kit was exposed to 38°C for two days, which may have damaged it and caused a false reactive result. Before issuing a final diagnosis, repeat the whole algorithm with a new kit that has been stored within the cold chain and record the kit lot and temperature. If the repeat is reactive, report as HIV-positive and link to care. If discordant, refer to a laboratory with EIA or nucleic acid testing.
2. What are the immediate clinical, prevention-of-mother-to-child-transmission and partner-notification actions, and what ethical and legal duties apply?
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Clinical action. If HIV infection is confirmed, start lifelong antiretroviral therapy for the mother regardless of CD4 count, using a national first-line regimen. Give infant nevirapine prophylaxis and arrange early infant diagnosis at the recommended age. Check baseline viral load, CD4, renal and liver function, and screen for TB and hepatitis.
Prevention and partners. Offer partner testing and supported disclosure; do not disclose without her consent unless required by law. Provide condoms and adherence counselling. Report the case to the national HIV programme as required, using a unique code. Maintain confidentiality. The ethical duties are consent, privacy, non-discrimination and linkage to care; the legal duty is reporting to public health, not to the partner without consent.
3. The repeat algorithm is reactive. The woman asks whether the first result could have been a false positive and whether she can refuse to tell her partner. How should you respond?
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Response. A false positive is possible, especially with a compromised kit, so the repeat algorithm matters. Explain that HIV tests detect antibodies and can be falsely reactive, and that confirmation with a properly stored kit or a supplemental test is needed. Do not say she is definitely infected until the repeat is complete, but do not reassure her that she is negative either.
Partner disclosure. She has a legal right to confidentiality. Partner notification should be voluntary and supported by counselling; the provider should not tell her partner without her consent unless a specific law requires it. Discuss the benefits of disclosure, offer to help, and provide her with time. If she refuses, document the counselling and continue to offer support. Report the confirmed case to the surveillance system confidentially.