Combo Test (Combined Rapid Diagnostic Test)


🧪 1. Objective
The objective of a combo test was to simultaneously detect two or more pathogens or biomarkers in a single patient sample using one device. This helped in rapid diagnosis of co-infections or differential diagnosis.

🧪 2. Principle
Combo tests typically used immunochromatographic (lateral flow) technology. Specific antibodies were embedded on a test strip or cassette to capture target antigens or antibodies from the sample. Colored lines indicated the presence or absence of the targets.

Example:

  • Dengue NS1 + IgM/IgG Combo

  • HIV 1/2 + HCV Combo

  • COVID-19 Ag + Influenza A/B Combo

  • Typhoid IgG/IgM + Malaria Combo

🧪 3. Materials

  • Combo rapid test cassette

  • Buffer solution

  • Capillary blood, serum, plasma, or swab sample

  • Dropper or pipette

  • Gloves and timer

🧪 4. Procedure

  1. The sample was collected (finger prick blood, serum, or swab).

  2. 2–3 drops of the sample were added to the sample well of the test cassette.

  3. Buffer drops were added to enhance flow.

  4. The cassette was left on a flat surface for 10–15 minutes.

  5. Results were read based on the appearance of colored lines at specific test zones (e.g., T1, T2, C).

🧪 5. Result (Example: Dengue + Malaria Combo)

Test AreaResultInterpretation
Dengue NS1PositiveAcute dengue infection
Dengue IgMNegativeNo current immune response
Malaria (Pf)NegativeNo Plasmodium falciparum detected
Control LinePresentTest valid

🧪 6. Uses

  • Fast, point-of-care diagnosis of multiple infections

  • Early detection in endemic areas or during outbreaks

  • Reduced cost and time vs. running multiple individual tests

  • Useful in ER, travel clinics, and field settings

🧪 7. Conclusion
Combo tests offered an efficient, accurate, and rapid way to screen for co-infections or similar presenting diseases. Their simplicity and speed made them essential tools in modern diagnostic protocols.

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