Evaluation of the polymerase chain reaction analysis for diagnosis of falciparum malaria in Delhi, India

Repeated sampling improved the sensitivity of malaria microscopy in children under six years

OBJECTIVE

Microscopy remains the gold standard for identification of malaria parasites. However, the sensitivity of malaria microscopy is low. This study evaluated the impact of repeated sampling up to 12 h in 177 children < 6 years with suspected malaria.

RESULTS

The median age was 3 years (interquartile range, 2.0-4.0 years). Eighty-nine percent (158/177) presented with hyperthermia together with one or more of the following symptoms: chills, headache, sweating, fatigue, nausea, abdominal pain, vomiting, diarrhea and cough. Baseline microscopy confirmed malaria in 29.9% (53/177) of the suspects. Repeated testing at 6 and 12 h increased the positive detection rates to 35.0% (62/177) and 41.8% (74/177), respectively. Microscopy underestimated malaria diagnosis by 11.9% on single testing. Children showing classical signs of malaria but with initial negative parasitological reports should be retested between 6 to 12 h to confirm or rule out a diagnosis of malaria.

Diagnostic Performance between Histidine-Rich Protein 2 (HRP-2), a Rapid Malaria Diagnostic Test and Microscopic-Based Staining Techniques for Diagnosis of Malaria

Malaria presents a diagnostic challenge in most tropical countries such as Rwanda. Microscopy remains the gold standard for diagnosing malaria, but it is labor intensive and depends upon the skill of the examiner. Malaria rapid diagnostic tests (RDTs) have been developed as an easy, convenient alternative to microscopy. This cross-sectional study was conducted at Rukara Health Center which is located in Eastern Province, Kayonza district, Rwanda. One hundred and fifty suspected cases of malaria, who attended Rukara Health Centre, during the period, from 21st June to 30th July 2018, were included in this study. HRP-2 RDTs (CareStart™ Malaria HRP-2 (Access Bio, Inc., Somerset, New Jersey, USA)), for malaria were performed. Thick smears were prepared and Giemsa-stained as recommended; then slides were observed under microscopy and reported quantitatively; RDTs were reported qualitatively (positive or negative). Both RDTs and thick smear results were recorded on data collection sheet. This study included a total of 150 study participants, 87 (58%) females and 63 (42%) males. The patients included in the study did not receive any antimalarial drug. The mean age of the study participants was 31.6 ± 12.4 with the majority of participants being between 25 and 44 years and the minority being above 65 years. The sensitivity of RDT (HRP-2) was calculated and found to be 95.0%, whereas the sensitivity of Giemsa microscopy was 100%. The specificity of RDT (HRP-2) was calculated and found to be 59.2%, whereas the specificity of Giemsa microscopy was 100%. Negative and positive predictive values of RDT are 85.4% and 82.7%, respectively. Negative and positive predictive values of Giemsa microscopy were both 100%. According to the results of the current study, the sensitivity, specificity, and both positive and negative predictive values of Giemsa microscopy are higher than those of histidine-rich protein 2-based rapid diagnostic test for malaria. The results obtained in histidine-rich protein 2-based rapid diagnostic test for malaria parasites should be confirmed with tests with high specificity. Further studies should determine the most appropriate type of rapid diagnostic test of malaria diagnosis to be used in combination with Giemsa microscopy. In addition, sensitivity and specificity of RDT (HRP-2) and Giemsa microscopy should be assessed against molecular biology techniques.

Malaria diagnosis by PCR revealed differential distribution of mono and mixed species infections by Plasmodium falciparum and P. vivax in India

Malaria is a vector-borne infectious disease, caused by five different species of the genus Plasmodium, and is endemic to many tropical and sub-tropical countries of the globe. At present, malaria diagnosis at the primary health care level in India is conducted by either microscopy or rapid diagnostic test (RDT). In recent years, molecular diagnosis (by PCR assay), has emerged as the most sensitive method for malaria diagnosis. India is highly endemic to malaria and shoulders the burden of two major malaria parasites, Plasmodium falciparum and P. vivax. Previous studies using PCR diagnostic assay had unraveled several interesting facts on distribution of malaria parasites in India. However, these studies had several limitations from small sample size to limited geographical areas of sampling. In order to mitigate these limitations, we have collected finger-prick blood samples from 2,333 malaria symptomatic individuals in nine states from 11 geographic locations, covering almost the entire malaria endemic regions of India and performed all the three diagnostic tests (microscopy, RDT and PCR assay) and also have conducted comparative assessment on the performance of the three diagnostic tests. Since PCR assay turned out to be highly sensitive (827 malaria positive cases) among the three types of tests, we have utilized data from PCR diagnostic assay for analyses and inferences. The results indicate varied distributional prevalence of P. vivax and P. falciparum according to locations in India, and also the mixed species infection due to these two species. The proportion of P. falciparum to P. vivax was found to be 49:51, and percentage of mixed species infections due to these two parasites was found to be 13% of total infections. Considering India is set for malaria elimination by 2030, the present malaria epidemiological information is of high importance.

Can Mixed Parasite Infections Thwart Targeted Malaria Elimination Program in India?

India is highly endemic to malaria with prevalence of all five species of human malaria parasites of Plasmodium genus. India is set for malaria elimination by 2030. Since cases of mixed Plasmodium species infections remain usually undetected but cause huge disease burden, in order to understand the distributional prevalence of both monospecies infections and mixed species infections in India, we collated published data on the differential infection incidences of the five different malaria parasites based on PCR diagnostic assay. About 11% of total cases were due to mixed species infection. Among several interesting observations on both single and mixed parasitic infections, incidences of Plasmodium falciparum monoinfection were found to be significantly higher than P. vivax monoinfection. Also, P. malariae seems to be emerging as a potential malaria threat in India. Putting all the facts together, it appears that the dream of achieving malaria elimination in India will not be completely successful without dealing with mixed species infection.

Detection of chloroquine and artemisinin resistance molecular markers in Plasmodium falciparum: A hospital based study

Introduction:

Emergence of chloroquine (CQ) resistance in Plasmodium falciparum has increased the morbidity and mortality of falciparum malaria worldwide. Artemisinin-based combination therapies are now recommended by the World Health Organization as the first line treatment for falciparum malaria. Numerous molecular markers have been implicated in the CQ and artemisinin resistance.

Materials and Methods:

A total of 26 confirmed cases of falciparum malaria (by giemsa stained thick and thin smear, quantitative buffy coat, immunochromatographic test, or polymerase chain reaction [PCR]) were included in the study. About 5 ml of ethylenediaminetetraacetic acid blood sample was collected and stored at −20°C till use. Plasmodium DNA was extracted using QIAamp whole blood DNA extraction kit. PCR was done to amplify pfcrt, pfmdr1, pfserca, and pfmrp1 genes and the amplicons obtained were sequenced by Macrogen, Inc., Korea. Single nucleotide polymorphism (SNP) analysis was done using Bio-Edit Sequence Alignment Editor.

Results:

Out of the four genes targeted, we noted a SNP in the pfcrt gene alone. This SNP (G > T) was noted in the 658^th position of the gene, which was seen in 13 patients. The pfmdr1 and pfserca genes were present in 9 and 14 patients respectively. But we could not find any SNPs in these genes. This SNP in pfcrt gene was not significantly associated with any adverse outcome and neither altered disease progression.

Conclusion:

Presence of a single SNP may not be associated with any adverse clinical outcome. As the sample size was small, we may have not been able to detect any other known or unknown polymorphisms.

A comparative laboratory diagnosis of malaria: microscopy versus rapid diagnostic test kits

OBJECTIVE

To compare the two methods of rapid diagnostic tests (RDTs) and microscopy in the diagnosis of malaria.

METHODS

RDTs and microscopy were carried out to diagnose malaria. Percentage malaria parasitaemia was calculated on thin films and all non-acute cases of plasmodiasis with less than 0.001% malaria parasitaemia were regarded as negative. Results were simply presented as percentage positive of the total number of patients under study. The results of RDTs were compared to those of microscopy while those of RDTs based on antigen were compared to those of RDTs based on antibody. Patients' follow-up was made for all cases.

RESULTS

All the 200 patients under present study tested positive to RDTs based on malaria antibodies (serum) method (100%). 128 out of 200 tested positive to RDTs based on malaria antigen (whole blood) method (64%), while 118 out of 200 patients under present study tested positive to visual microscopy of Lieshman and diluted Giemsa (59%). All patients that tested positive to microscopy also tested positive to RDTs based on antigen. All patients on the second day of follow-up were non-febrile and had antimalaria drugs.

CONCLUSIONS

We conclude based on the present study that the RDTs based on malaria antigen (whole blood) method is as specific as the traditional microscopy and even appears more sensitive than microscopy. The RDTs based on antibody (serum) method is unspecific thus it should not be encouraged. It is most likely that Africa being an endemic region, formation of certain levels of malaria antibody may not be uncommon. The present study also supports the opinion that a good number of febrile cases is not due to malaria. We support WHO's report on cost effectiveness of RDTs but, recommend that only the antigen based method should possibly, be adopted in Africa and other malaria endemic regions of the world.

Newer versus Conventional Methods in the Diagnosis of Malaria: A Comparison

BACKGROUND

This study attempts to evaluate and compare the efficacy of polymerase chain reaction (PCR) and quantitative buffy coat (QBC) assay with conventional Giemsa stained peripheral blood smear (PBS) examination in the diagnosis of malaria.

METHODS

The study was conducted on 50 cases of smear positive malaria (group 1), 50 cases of clinically suspected malaria (group 2) and 15 healthy controls. All were subjected to Giemsa stain slide examination both thick and thin smear, QBC assay and PCR. PBS examination by Giemsa stain was taken as gold standard.

RESULT

In this study the overall sensitivity and positive predictive value (PPV) of QBC assay in group 1 was 100% and that of PCR was 60% and 100% respectively. In group 2 the sensitivity, specificity, PPV and NPV of QBC assay was 100% and that of PCR was 71%, 100%, 100% and 73% respectively as compared to the gold standard. All the 15 healthy controls were negative by all the three assays showing 100% specificity.

CONCLUSION

QBC assay was an excellent alternative to the conventional method as it is rapid and less time consuming and can directly demonstrate the parasite. Utility of PCR lies in species-specific diagnosis of falciparum malaria especially when there is a high degree of clinical suspicion and the report is negative by the other two methods.