Study On The Application Of RDT, Microscopy Examination And PCR On Malaria

Objective To compare the sensibility, specificity and consistency among microscopicexamination, RDT and PCR in the diagnosis of malaria, and provide the basis for decidethat if RDT can replace microscopic examination in county level hospital. To comparethe sensibility, specificity and consistency among microscopic examination, domesticRDT, imported RDT and PCR in the diagnosis of malaria, and provide the basis fordecide that if domestic RDT can replace imported RDT or not. Continuous observingthe results of seven days detection which diagnosed malaria cases, calculating the timeto turn negative of microscopy, PCR and RDT, and the parasite density of the bloodsamples from different date to evaluate the sensibility, specificity and consistencyamong microscopic examination, RDT and PCR in the diagnosis of malaria in differentcourse. To provide the basis for the surveillance work in malaria elimination phase.Methods Two hundreds sixty seven suspected and confirmed blood samples and267blood smears, from January2012to September2013were collected and detected bymicroscopic examination, RDT and PCR. Then, all the results were compared in pairs.50cases non-malaria blood samples were collected from Furong community healthservice centre. All the malaria cases were investigated by epidemiological questionnaireto understand the general situation. CareStartTMMalaria HRP2/PLDH Combo Test,Wondfo rapid diagnostic tests and ABI7500Real-Time PCR amplification were used todetect blood samples.37definite malaria cases were collected from Anhui provincial hospital and Anhui Feidong province people’s hospital during May2013to September2013. Continuous7days blood samples were extracted from every malaria case. If casewas hospitalized less than7days, taking the PCR and microscopy has the time to turnnegative as standard. Microsoft Excel2007, Epidata3.1and SPSS11.5were used tocollect and manage the data. Wilcoxon test, chi-square test were used to analyzed thedata.Results A total of267samples was tested; microscopy examination check out148positive case, positive rate was55.43%, P.f is117, P.v is20, P.o is10, P.m is1; PCRcheck out150positive case, positive rate is56.18%, P.f is119(including117cases ofmicroscopy detection), P.v is20, P.o is10, P.m is1; RDT check out147positive case,positive rate is55.06%, P.f is126(including microscopic examination for114cases ofP.f, and the other microscopic examination of the12cases were negative; PCR test for116cases of plasmodium falciparum, and the other10cases of PCR test negative),non-P.f is21(including19P.v cases and2P.f cases of microscopy and PCR detection).Therefore, imported RDT was not detected in1P.v and1case of P.f, and2cases of P.finspection for P.v,10cases of PCR and microscopy are checked for negative casedetection of P.f,10cases of P.o and1cases of P.m are not checked out three days. FromFurong community health service station of50cases of malaria RDT, microscopy andPCR detection are all negative. Compared to microscopy, the sensitivity of RDT was98%, specificity90%, false positive rate10%, false negative rate2%, positivepredictive value92%, negative predictive value98%; Compared to PCR, the sensitivityof RDT was98%, specificity91%, false positive rate9%, false negative rate2%,positive predictive value93%, negative predictive value98%. Compared domestic RDTto imported RDT, results of domestic and imported RDT statistic in consistency check,there was no statistically significant difference(2=4.000, P＞0.05). Kappa value is0.97,P＜0.001. The median of the time turn to negative of microscopy examination is2days, and the median of the time turn to negative of PCR is3days. Wilcoxon tests showedthat the difference on the median of the time turn to negative between microscopy andPCR was statistically significant(Z=3.776, P＜0.05). The time turn to negative ofmicroscopy were different which from1to5days,16of the cases turn to negative whenthe second day. The median of the parasite density of the one day turn to negative groupis3571/μl blood, and the2to5days group is38385/μl blood,11456/μl blood and147/μl blood which on a declining curve.Conclusions Results indicate that RDT product used in this study cannot detect in P.oand P.m. The sensitivity and specificity of RDT are very high, and overwhelmingmajority of P.v and P.f can be detected by RDT. Hence, RDT can totally replacemicroscopic examination to diagnose malaria in low malaria epidemic period. DomesticRDT can replace imported RDT to support active surveillance system. The median ofthe time turn to negative of microscopy examination is2days; the median of the timeturn to negative of PCR is3days; and RDT is more than7days. Change of parasite ofmalaria can be used as a clinical index to judge treatment effect.