Malaria diagnosis: Addressing the issue of HRP2 gene deletions (UPDATED VERSION)

Summary

Malaria causes over 600,000 deaths annually, and timely diagnosis is crucial to prevent severe outcomes. WHO recommends using rapid diagnostic tests (RDTs), which detect malaria antigens in blood quickly and accurately. However, mutations in the Plasmodium falciparum parasite can cause RDTs to miss cases. HRP2-based tests are particularly affected, as the parasite can lack the HRP2 gene. WHO advises regular surveillance, investigating HRP2 gene deletions, and switching to alternative RDTs when necessary. With continued research and development, new diagnostic solutions are on the horizon to improve malaria control globally.

Takeaways

• 😀 Malaria claims over 600,000 lives annually, making timely diagnosis critical to saving lives.
• 😀 WHO recommends using quality-assured microscopy or rapid diagnostic tests (RDTs) for malaria diagnosis.
• 😀 RDTs provide results in just 15-30 minutes and are user-friendly, accurate, and affordable.
• 😀 The widespread use of RDTs has significantly improved malaria clinical care and saved millions of lives.
• 😀 RDTs help track malaria prevalence over time, enabling targeted interventions by national malaria control programs.
• 😀 P. falciparum, the deadliest malaria parasite, is typically detected using the HRP2 antigen in RDTs.
• 😀 Mutations causing the HRP2 antigen gene deletion in P. falciparum have been reported in 37 countries.
• 😀 HRP2 gene deletions lead to false negative results, putting millions at risk of undiagnosed or misdiagnosed malaria.
• 😀 In some areas of Africa, up to 80% of P. falciparum cases may go undetected due to HRP2 deletions.
• 😀 WHO recommends surveillance and investigation of HRP2 deletions and suggests switching to alternative RDTs when 5% or more of P. falciparum cases are missed.
• 😀 WHO tracks HRP2 deletions globally using the Malaria Threats Map, guiding surveillance efforts and prioritizing areas for intervention.

Q & A

What is malaria, and why is timely diagnosis crucial?

Malaria is a life-threatening disease that claims over 600,000 lives annually. Timely diagnosis is critical to preventing the infection from progressing to severe illness and death.

What are Rapid Diagnostic Tests (RDTs), and how do they work?

RDTs are diagnostic tools designed to detect antigens in a person's blood, with results available in 15 to 30 minutes. They are user-friendly, accurate, and affordable, helping to diagnose malaria quickly, especially in areas with limited access to microscopy services.

How have RDTs improved malaria diagnosis over the past 15 years?

RDTs have significantly improved clinical care for millions of people with malaria symptoms, increasing knowledge of where malaria is prevalent and allowing targeted interventions to control the disease.

What is the role of RDTs in monitoring malaria prevalence?

RDTs have helped improve understanding of malaria's geographic spread, allowing national malaria control programs to better target interventions to control the disease.

How does the Plasmodium falciparum parasite evade detection by RDTs?

Plasmodium falciparum parasites can evade detection if they lack the gene encoding for the histidine-rich protein 2 (HRP2), a key antigen targeted by many RDTs, leading to false-negative results.

What is the significance of HRP2 gene deletions in malaria diagnosis?

HRP2 gene deletions cause false-negative RDT results because the antigen is no longer produced, preventing detection of the parasite in blood samples.

Where have HRP2 gene deletions been reported, and how does this impact malaria diagnosis?

HRP2 gene deletions have been reported in 37 countries, mainly in South America and Africa. In some regions, RDTs may miss 60 to 80 percent of P. falciparum malaria cases, increasing the risk of delayed diagnosis or misdiagnosis.

What can be done to address the problem of HRP2 gene deletions in malaria diagnosis?

To address HRP2 gene deletions, regular surveillance should be established, and suspicious reports from the field should be investigated. WHO recommends switching to RDTs that detect alternative antigens once more than 5% of P. falciparum cases are missed due to HRP2 deletions.

What role does WHO play in tracking and addressing HRP2 gene deletions?

WHO tracks reports of HRP2 gene deletions and posts them on the malaria threats map platform, helping inform surveillance activities and prioritize areas for intervention.

What options exist for detecting malaria if HRP2-based RDTs are ineffective?

Non-HRP2-based test options are limited but do exist. Research and development efforts are underway to create more effective tests that can address HRP2 deletions and improve malaria detection.