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This page describes products and general use; it is not medical advice.
What a rapid diagnostic test is
A rapid diagnostic test (RDT) is a device that detects a marker of a condition in a specimen and returns a result within minutes. WHO describes malaria RDTs as relatively simple to perform and interpret, quick to give results, and needing limited training, which allows diagnosis at community level and in remote areas where good microscopy is hard to provide. For malaria, blood is commonly taken by finger-prick and results are available within 15–30 minutes.
Who uses it: health workers and clinic staff (WHO), and, for HIV point-of-care serology tests in the United States, professional users acting for a clinical laboratory (21 CFR 866.3956).
The best-documented family is malaria. Manufacturers surveyed for the World malaria report 2023 reported 3.9 billion malaria RDTs delivered between 2010 and 2022, more than 82% of them to sub-Saharan Africa, and WHO counts more than 200 malaria RDT products on the market. The device category is also part of the wider in vitro diagnostic field, covered in what an in vitro diagnostic is.
How a rapid diagnostic test is built and works
WHO describes malaria RDTs as lateral flow immunochromatographic antigen-detection tests. Products vary in targets and formats, but the principles are similar. The parts WHO names:
- Cassette: a plastic housing around a strip of filter paper and nitrocellulose.
- Sample well and buffer well: blood goes into one hole (A) and buffer into another (B); the buffer carries the blood along the strip.
- Lysing agent: ruptures red blood cells, releasing more parasite protein.
- Dye-labelled antibody: specific for the target antigen, held on the lower end of the strip or in a plastic well supplied with it.
- Test line (T): antibody bound in a thin line; if antigen is present, labelled antibody-antigen complex accumulates there and becomes visible.
- Control line (C): shows that labelled antibody travelled the full strip and that some capture properties remain intact.
At low parasite densities the test-line intensity varies with the amount of antigen. At higher densities the control line can fade because much of the labelled antibody is captured at the test line before it arrives. For strip-level detail such as labels and sandwich versus competitive formats, see lateral flow test: how the strip is built.
Types and variants
| Family | What it detects | Key difference | Reference |
|---|---|---|---|
| Malaria antigen RDT | Parasite antigens in blood; FDA’s definition names HRP2 and pan-malarial antigens in whole blood | Some detect one species (P. falciparum or P. vivax), some several species, some separate P. falciparum from non-P. falciparum | WHO; FDA Class II, 21 CFR 866.3402, product code OAX |
| HIV point-of-care serology test | HIV antigen(s) and/or antibodies against HIV in body fluids or tissues, qualitatively | Prescription device for professional use only; reactive results are preliminary | FDA Class II, 21 CFR 866.3956, product code QSU |
| G6PD RDT | G6PD deficiency (glucose-6-phosphate dehydrogenase) | Not an infection test; WHO’s guide links it to P. vivax radical cure | WHO training manual and programme guide, 2018 |
Single-product explainers on CASRAI include the rapid strep test.
Specifications and standards that matter
Performance numbers are specific to a test family and a stated condition. WHO’s minimum requirements below apply to malaria RDTs when no appropriate WHO-prequalified test is available, for example in settings with at least 5% prevalence of pfhrp2/3 gene deletions that cause negative HRP2-RDT results.
| Item | Value stated | Source |
|---|---|---|
| Quality system | ISO 13485 certified | WHO |
| Panel detection score | At least 75% at 200 parasites/µL (P. falciparum HRP2-expressing and non-HRP2-expressing panels; P. vivax if applicable) | WHO |
| False positive rate | Less than 10% | WHO |
| Invalid tests | Fewer than 5% | WHO |
| Thermal stability | High thermal stability recommended for very hot areas, ideally 40–45 °C | WHO |
| HIV point-of-care clinical performance | For tests intended solely for point-of-care use, lower bound of the 95% confidence interval at least 98% for both clinical sensitivity and clinical specificity | 21 CFR 866.3956(b)(2) |
WHO adds that the panel detection score is not the same as sensitivity: sensitivity is measured in a real population with a mix of high- and low-density infections, while the score reflects performance at the lower limit of clinically significant parasitemia.
How to choose: criteria stated by WHO and FDA
| Question | Criterion stated | Source |
|---|---|---|
| Is it WHO-prequalified? | WHO recommends that all RDTs for procurement be prequalified; prequalified products meet the required minimum performance criteria, and each malaria RDT has a public report on the assessment and manufacturing-site inspection | WHO |
| Does a higher score help? | Products exceeding the minimum criteria are not expected to have any significant clinical benefit over those that just meet them | WHO |
| Is it for hot storage or use? | Select RDTs with high thermal stability for very high ambient temperature, ideally 40–45 °C | WHO |
| Is the specimen type cleared? | HIV test labelling must state the matrices cleared, and that other specimen types may give inaccurate results | 21 CFR 866.3956(b)(1) |
| Is it labelled for the intended user? | HIV point-of-care labelling must state point-of-care use, distribution to clinical laboratories with a quality assurance programme, and use only by an agent of a clinical laboratory | 21 CFR 866.3956(b)(2) |
WHO prequalification of in vitro diagnostics, launched in 2010, covers dossier assessment, labelling review and manufacturing-site inspection. Under WHO’s notice, from 2026 performance evaluation is no longer part of the prequalification assessment and becomes a separate procedure.
Safe use and handling basics
- Use the manufacturer’s instructions for use for the specific product. FDA’s special controls require HIV test labelling to include the principles of operation, the procedure for performing the assay and how to interpret results.
- WHO publishes training manuals and job aids for the safe and accurate use of malaria RDTs, a 2022 guide to quality and safety practices for malaria rapid testing services, and 2019 guidance on control materials for antigen-detecting malaria RDTs.
- For how point-of-care testing is handled in US laboratories, see CLIA-waived point-of-care testing and the broader point-of-care testing guide.
Common mistakes
- Reading the panel detection score as sensitivity. WHO says they are different measures.
- Treating a visible control line as proof the test can detect the target. WHO states the control line shows the integrity of the antibody-dye conjugate, not the ability to detect parasite antigen.
- Assuming one antigen target works everywhere. pfhrp2/3 gene deletions cause negative HRP2-RDT results, and WHO’s minimum-requirements pathway names settings with at least 5% prevalence of such deletions as its example.
- Treating a nonreactive HIV result as ruling out infection. FDA’s required limitations say it does not exclude exposure or infection, and a reactive result should be investigated further; point-of-care reactive results are preliminary.
- Assuming a higher-scoring product is clinically better. WHO does not expect significant clinical benefit above the minimum criteria.
FAQ
What does rapid testing mean?
Rapid describes time to result and setting: in WHO’s malaria example, simple tests that give results in 15–30 minutes with limited training. It does not mean unregulated: FDA classifies the malaria antigen and HIV point-of-care families as Class II devices with special controls.
What is the full meaning of RDT?
RDT stands for rapid diagnostic test, as in WHO’s “malaria rapid diagnostic tests (RDTs)”.
What are the 8 key diagnostic tests?
“Key diagnostic tests” is not a fixed regulatory category, and FDA classifies devices by type, such as the two RDT families above. MedlinePlus’s Diagnostic Tests topic page lists entries including laboratory tests, diagnostic imaging, endoscopy, genetic testing, biopsy and vital signs; which of them matter depends on the clinical question.
What are four types of diagnostic testing and give an example?
Using MedlinePlus’s Diagnostic Tests topic page: laboratory tests (for example blood tests), diagnostic imaging (X-rays, CT scans, MRI scans), vital signs (blood pressure, temperature) and genetic testing (paternity testing). An RDT is a laboratory-type in vitro test; FDA files the malaria and HIV families under immunology and microbiology devices (21 CFR Part 866).
Sources
- WHO Global Malaria Programme, Rapid diagnostic tests, read 2026-11-07.
- WHO Global Malaria Programme, How malaria RDTs work, read 2026-11-07.
- WHO Prequalification, In Vitro Diagnostics, read 2026-11-07.
- FDA via Cornell LII, 21 CFR 866.3402, Plasmodium species antigen detection assays, read 2026-11-07.
- FDA via Cornell LII, 21 CFR 866.3956, HIV serological diagnostic and/or supplemental test, read 2026-11-07.
- FDA, openFDA device classification records (product codes OAX and QSU), read 2026-11-07.
- MedlinePlus, Diagnostic Tests, read 2026-11-07.
