|1.||Malar J. 2013 May 21;12(1):167. [Epub ahead of print]|
Routine parallel diagnosis of malaria using microscopy and the malaria rapid diagnostic test SD 05FK60: the experience of Medecins Sans Frontieres in Myanmar.Kosack CS, Naing WT, Piriou E, Shanks L.
Malaria rapid diagnostic tests (RDTs) are commonly used in Medecins Sans Frontieres (MSF) programmes to detect acute malaria infection. Programmes in regions with both Plasmodium falciparum and non-falciparum malaria (i.e. Plasmodium ovale, Plasmodium malariae and Plasmodium vivax) use a three-band P. falciparum/Pan test such as the SD Bioline Malaria Ag P.f/Pan 05FK60 (Standard Diagnostics, Kyonggi, Republic of Korea), hereafter referred to as SD 05FK60, as used by the MSF-Holland clinics in Rakhine state, Myanmar. In spite of published reports of generally good test performance, medical and paramedical staff on the ground often doubt the diagnostic accuracy of these RDTs.
Parallel testing with malaria microscopy and RDT was conducted at two clinics in Rakhine state, Myanmar, for a period of 14 months as a programmatic response due to doubts and concerns of medical and paramedical staff into malaria RDTs.
A total of 2,585 blood samples from non-pregnant suspected malaria patients were examined by the SD 05FK60 RDT and microscopy at two clinics in Myanmar from October 2010 to December 2011. The reference standard microscopy diagnosed 531 P. falciparum and 587 P. vivax or P. malariae mono-infections. The overall sensitivity for P. falciparum detection by the SD 05FK60 was 90.2% (95% CI: 87.4-92.6) and for P. vivax/P. malariae 79.4% (95% CI: 75.9-82.6). The overall specificity for P. falciparum detection by the SD 05FK60 was 98.5% (95% CI: 97.7-99.1) and for P. vivax/P. malariae 98.7% (95% CI: 97.9-99.2). The sensitivity for P. falciparum was >91% for parasitaemia levels of >100-1,000 parasites/mul and increased for P. vivax/P. malariae with the parasitaemia level but was overall lower than for P. falciparum.25/408 and 13/420 cases, respectively, of P. falciparum and non-falciparum malaria were missed by the RDT.
In field conditions in Myanmar, the SD 05FK60 malaria RDT performed consistent with other reports. The test detected malaria caused by P. vivax/P. malariae to a lesser extent than P. falciparum infection. Sensitivity improved with increasing parasitaemia level, however even at higher levels some infections were missed. The SD 05FK60 is adequate for use in settings where high quality microscopy is not available.
|PMID: 23692957 [PubMed - as supplied by publisher]|
|2.||Malar J. 2013 May 21;12(1):166. [Epub ahead of print]Shin HI, Kim JY, Lee WJ, Sohn Y, Lee SW, Kang YJ, Lee HW.|
Assaying for the parasitic lactate dehydrogenase (pLDH) is widely used as a rapid diagnostic test (RDT), but the efficacy of its serological effectiveness in diagnosis, that is antibody detection ability, is not known. The genetic variation of Korean isolates was analysed, and recombinant protein pLDH was evaluated as a serodiagnostic antigen for the detection of Plasmodium vivax malaria.
Genomic DNA was purified, and the pLDH gene of P. vivax was amplified from blood samples from 20 patients. The samples came from five epidemic areas: Bucheon-si, Gimpo-si, and Paju-si of Gyeonggi Province, Gangwha-gun of Incheon metropolitan city, and Cheorwon-gun of Gangwon Province, South Korea, from 2010 to 2011. The antigenicity of the recombinant protein pLDH was tested by western blot and enzyme-linked immunosorbent assay (ELISA).
Sequence analysis of 20 Korean isolates of P. vivax showed that the open reading frame (ORF) of 951 nucleotides encoded a deduced protein of 316 amino acids (aa). This ORF showed 100% identity with the P. vivax Belem strain (DQ060151) and P. vivax Hainan strain (FJ527750), 89.6% homology with Plasmodium falciparum FCC1_HN (DQ825436), 90.2% homology with Plasmodium berghei (AY437808), 96.8% homology with Plasmodium knowlesi (JF958130), and 90.2% homology with Plasmodium reichenowi (AB122147). A single-nucleotide polymorphism (SNP) at nucleotide 456 (T to C) was also observed in the isolate from Bucheon, but it did not change in the amino acid sequence. The expressed recombinant protein had a molecular weight of approximately 32 kDa, as analysed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis. Of the 40 P. vivax patients, 34 (85.0%) were positive by ELISA.
The pLDH genes of 19 isolates of P. vivax were identical, except one for SNP at nucleotide 456. This observation indicates that this gene is relatively stable. Based on these results, the relationship between antibody production against pLDH and the pattern of disease onset should be investigated further before using pLDH for serodiagnosis.
|PMID: 23688062 [PubMed - as supplied by publisher]|
|3.||Malar J. 2013 May 10;12(1):159. [Epub ahead of print]|
Over-diagnosis of malaria by microscopy in the Kilombero Valley, Southern Tanzania: an evaluation of the utility and cost-effectiveness of rapid diagnostic tests.Harchut K, Standley C, Dobson A, Klaassen B, Rambaud-Althaus C, Althaus F, Nowak K.
Early and accurate diagnosis of febrile patients is essential to treat uncomplicated malaria cases properly, prevent severe malaria, and avert unnecessary anti-malarial treatments. Improper use of anti-malarials increases the risk of adverse drug reaction and the evolution of drug/parasite resistance. While microscopy is the most common form of malaria diagnosis, concerns over its accuracy have prompted the incorporation of malaria rapid diagnostic tests (RDTs) into many national malaria control programmes.
Over a three-month period, a direct comparison between microscopy and RDTs was made in a rural, private dispensary in the Kilombero Valley, Morogoro District, southern Tanzania, with the aim of estimating the extent of malaria over-diagnosis and over-treatment with anti-malarials. The study cohort was made up of patients referred by the dispensary's clinician for malaria testing. One hundred percent of patients approached agreed to participate in this study and were then tested using both microscopy and RDTs. Using the results from the comparison of the two tests at this dispensary, the potential cost effectiveness of introducing RDTs to a neighbouring public health centre was estimated on the basis of this centre's past malaria records spanning December 2007 to August 2011.
At the private dispensary, the apparent prevalence of malaria was 78% based on microscopy whereas the true prevalence, calculated using RDTs as the gold standard, was estimated at 14%. This discrepancy indicates that when using microscopy as the sole diagnostic test, malaria is being over-diagnosed by approximately a factor of five in this setting. At the public clinic, apparent malaria prevalence based on microscopy was 74%. If similar rates of over-diagnosis are assumed, 5,285 patients of the 6,769 patients positively diagnosed with malaria using microscopy were likely given unnecessary anti-malarials, and their true cause of illness was not addressed. The introduction of RDTs to the public clinic would be highly cost-efficient, with an estimated net saving of over 96 USD/month.
Compared with RDTs, microscopy led to almost four out of five patients being over-diagnosed with malaria in this rural part of Tanzania. A policy that encompasses both the private and public sectors of health care is needed to ensure quality diagnostic testing for febrile patients. With estimated prevalence at 14%, RDT introduction is recommended given WHO findings that RDTs are predicted to be cost-effective in prevalence areas of less than 20%. The use of RDTs in malaria diagnosis would not only reduce government spending but would prove beneficial to ensuring appropriate care and treatment of febrile illness.
|PMID: 23663437 [PubMed - as supplied by publisher]|