Utility of pf/pan RDT for diagnosis in the prevention of re-establishment o f malaria in Sri Lanka

The utility of CareStart (TM) Malaria Pf/PAN (HRP2/pLDH) Ag Combo Test, in detecting non-endemic clinical malaria cases was evaluated in Sri Lanka, a country in prevention of reestablishment of malaria following elimination. RDT, microscopy and nested PCR were performed for 350 suspected malaria patients recruited prospectively. There were 173 PCR confirmed malaria patients and 177 PCR negative subjects. Plasmodium falciparum amounted to 48% of infections with 44% P. vivax, 6% P. ovale and 2% P. malariae. Performance characteristics of RDTs and microscopy were compared with nested PCR. Sensitivity and specificity of RDT with 95% confidence intervals (CI) were as follows: any malaria infection 95.95% (CI = 91.84-98.36) and 94.92% (CI = 90.57-97.65); P. falciparum 100% (CI = 95.65-100) and 97.00% (CI = 94.18-98.70) and other species 92.22% (CI = 84.63-96.82) and 99.62% (97.88-99.99) respectively. A significant difference between sensitivities of HRP2 (100%, CI = 95.65-100) and pan pLDH line (68.67%, CI = 57.56-78.41) was seen for P. falciparum, parasite densities less than 1000 parasites/microliter being detected only by HRP2. Sensitivity and specificity of microscopy with 95% CI were as follows: any malaria infection, 94.22% (CI = 89.63-97.19) and 99.44% (CI = 96.89-99.99); P. falciparum 89.16% (CI = 80.40-94.90) and 99.63% (CI = 97.94-99.99); other species 98.89% (CI = 93.96-99.97) and 100% (CI = 98.59-100) respectively. The low sensitivity of pan specific pLDH for P. falciparum, P. ovale and P. malariae should be taken in to consideration when using this RDT as a point of care test when and wherever microscopy facilities are not readily available. Considering the low sensitivity of microscopy for P. falciparum, it is preferable to perform both tests, when malaria is highly suspected.