Evaluation of a real-time polymerase chain reaction assay for the diagnosis of malaria in patients from Jazan area, Saudi Arabia

J Egypt Soc Parasitol. 2008 Aug;38(2):339-50.

Abstract

A real-time PCR assay with conventional microscopy by Giemsa-stained blood films was used. PCR was completed in an hour and identified the Plasmodium species in a single reaction. Blood was collected, and DNA was extracted. A genus-specific primer set corresponding to 18S ribosomal RNA was used to amplify target sequence. Fluorescence resonance energy technology hybridization probes were designed for P. falciparum over a region containing base pair mismatches allowed Plasmodium species differentiation. Microscopically positive patients (n = 60) were positive with real-time assay (100% sensitivity). 58 were single-species infections caused by P. falciparum; mixed infections (P. falciparum & P. vivax) were shown by real-time assay. Six out of 30 negative microscopy specimens were positive by real-time PCR (80% specificity). The discrepant results could be due to the subjective nature of microscopy and analytical objectivity of PCR, and high analytical sensitivity of real-time assay (1 parasite/microl) compared to microscopy (50 parasites/microl). Six patients were retested with ICT malaria test and 4 were positive showing that PCR results were correct. There was low correlation between parasitemia by microscopy and gene copy number for P. falciparum (r = 0.2; P = 0.05 [Spearman]).

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Blood Specimen Collection
  • DNA, Protozoan / analysis*
  • DNA, Protozoan / chemistry
  • DNA, Protozoan / genetics
  • Gene Amplification
  • Humans
  • Malaria / diagnosis*
  • Malaria / parasitology
  • Microscopy
  • Parasitemia / diagnosis
  • Plasmodium / isolation & purification*
  • Polymerase Chain Reaction / methods*
  • RNA, Ribosomal, 18S / chemistry
  • RNA, Ribosomal, 18S / genetics
  • Saudi Arabia
  • Sensitivity and Specificity
  • Species Specificity

Substances

  • DNA, Protozoan
  • RNA, Ribosomal, 18S