Buffer substitution in malaria rapid diagnostic tests causes false-positive results

Area of Science:

• Medical Diagnostics
• Parasitology
• Public Health

Background:

• Malaria rapid diagnostic tests (RDTs) are crucial for malaria diagnosis in resource-limited settings.
• RDT kits typically include a specific buffer solution, but field conditions often lead to its unavailability.
• Laboratory staff sometimes substitute the buffer with readily available liquids like saline, distilled water, or tap water.

Purpose of the Study:

• To evaluate the impact of using common substitute liquids as buffers on the accuracy of malaria rapid diagnostic tests.
• To determine if buffer substitution affects the reliability and validity of RDT results.

Main Methods:

• Twenty-seven different RDT brands were tested using blood samples from malaria-negative individuals.
• Saline, distilled water, and tap water were used as substitute buffers for the RDTs.
• Results were compared against those obtained using the manufacturer's buffer and Plasmodium-positive samples.

Main Results:

• False-positive test lines appeared in 74% of RDT brands when using substitute liquids (saline, distilled water, tap water).
• These false positives occurred across all Plasmodium antigens and RDT formats.
• The visual quality of the false-positive lines was comparable to true positives, potentially leading to misdiagnosis.

Conclusions:

• Substituting the RDT kit's buffer with saline, distilled water, or tap water can lead to false-positive malaria test results.
• This highlights the critical importance of using the correct buffer solution for accurate malaria diagnosis with RDTs.