VHOSPITAL.CLINIC · Diagnostic Test
Blood PCR is the most sensitive method for malaria detection, identifying Plasmodium at parasitaemia levels below 1 parasite/μL — essential for species confirmation, mixed infections, and drug resistance profiling.
PCR amplifies Plasmodium-specific 18S rRNA or species-specific genes from peripheral blood DNA. It is the reference standard for species identification, detecting submicroscopic infections that blood smear and RDT miss.
EDTA blood (1–3 mL) is collected. DNA is extracted, and real-time or nested PCR targets species-specific sequences. Multiplex PCR can simultaneously identify all four Plasmodium species plus P. knowlesi. Results in 4–24 hours depending on platform.
Species-specific bands/Ct values confirm the infecting species and allow quantification. Mixed infections (e.g., P. falciparum + P. vivax) are detected. Resistance gene analysis (pfkelch13 for artemisinin; pfcrt for chloroquine) can be added.
Sensitivity: >99% for parasitaemia >1 parasite/μL. Detects submicroscopic infection (1–100 parasites/μL) missed by smear and RDT. Specificity: >99.5%. PCR remains positive longer than RDT after treatment.
Not always. For uncomplicated falciparum malaria in an endemic setting, blood smear is sufficient to start treatment. PCR is added when species is uncertain, mixed infection is suspected, treatment failure occurs, or epidemiological data is needed.
Yes. PCR detects Plasmodium at parasitaemia levels of 1–5 parasites/μL — several days earlier than blood smear (which typically requires >100 parasites/μL for reliable detection). This is valuable in the pre-symptomatic phase of infection.
PCR may remain positive for 1–4 weeks after clinically effective treatment as it detects parasite DNA from lysed cells. A positive PCR at day 28 with clinical symptoms suggests treatment failure; positive PCR alone without symptoms requires clinical correlation.
Blood PCR helps confirm Malaria, which can cause these symptoms:
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