title: Evaluation of the malaria rapid diagnostic test SDFK90: detection of both PfHRP2 and Pf-pLDH.
abstract: BACKGROUND
  Rapid diagnosis of Plasmodium falciparum infections is important because of the potentially fatal complications. SDFK90 is a recently marketed malaria rapid diagnostic test (RDT) targeting both histidine-rich protein 2 (PfHRP2) and P. falciparum-specific Plasmodium lactate dehydrogenase (Pf-pLDH). The present study evaluated its diagnostic accuracy.
  
  
  METHODS
  SDFK90 was tested against a panel of stored whole blood samples (n= 591) obtained from international travellers suspected of malaria, including the four human Plasmodium species and Plasmodium negative samples. Microscopy was used as a reference method, corrected by PCR for species diagnosis. In addition, SDFK90 was challenged against 59 P. falciparum samples with parasite density ≥4% to assess the prozone effect (no or weak visible line on initial testing and a higher intensity upon 10-fold dilution).
  
  
  RESULTS
  Overall sensitivity for the detection of P. falciparum was 98.5% and reached 99.3% at parasite densities >100/μl. There were significantly more PfHRP2 lines visible compared to Pf-pLDH (97.3% vs 86.9%), which was mainly absent at parasite densities <100/μl. Specificity of SDFK90 was 98.8%. No lot-to-lot variability was observed (p = 1.00) and test results were reproducible. A prozone effect was seen for the PfHRP2 line in 14/59 (23.7%) P. falciparum samples tested, but not for the Pf-pLDH line. Few minor shortcomings were observed in the kit's packaging and information insert.
  
  
  CONCLUSIONS
  SDFK90 performed excellent for P. falciparum diagnosis. The combination of PfHRP2 and Pf-pLDH ensures a low detection threshold and counters potential problems of PfHRP2 detection such as gene deletions and the prozone effect.
authors.affiliation: Department of Clinical Sciences, Institute of Tropical Medicine, Antwerp, Belgium.
authors.forename: Marloes
authors.initials: M
authors.lastname: Heutmekers
authors.forename: Philippe
authors.initials: P
authors.lastname: Gillet
authors.forename: Lieselotte
authors.initials: L
authors.lastname: Cnops
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Bottieau
authors.forename: Marjan
authors.initials: M
authors.lastname: Van Esbroeck
authors.forename: Jessica
authors.initials: J
authors.lastname: Maltha
authors.forename: Jan
authors.initials: J
authors.lastname: Jacobs
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000953:Antigens, Protozoan / Q000097:blood*; D002648:Child; D002675:Child, Preschool; D003955:Diagnostic Tests, Routine / Q000379:methods*; D005260:Female; D006801:Humans; D007223:Infant; D007770:L-Lactate Dehydrogenase / Q000097:blood*; D016778:Malaria, Falciparum / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D010963:Plasmodium falciparum / Q000276:immunology* / Q000302:isolation & purification; D015800:Protozoan Proteins / Q000097:blood*; D012680:Sensitivity and Specificity; D055815:Young Adult
chemical_list: D000953:Antigens, Protozoan; C514457:HRP-2 antigen, Plasmodium falciparum; D015800:Protozoan Proteins; D007770:L-Lactate Dehydrogenase