Diagnostic performance of rapid diagnostic tests versus blood smears for malaria in US clinical practice.
BACKGROUND
Approximately 4 million US travelers to developing countries are ill enough to seek health care, with 1500 malaria cases reported in the United States annually. The diagnosis of malaria is frequently delayed because of the time required to prepare malaria blood films and lack of technical expertise. An easy, reliable rapid diagnostic test (RDT) with high sensitivity and negative predictive value (NPV), particularly for Plasmodium falciparum, would be clinically useful. The objective of this study was to determine the diagnostic performance of a RDT approved by the US Food and Drug Administration compared with traditional thick and thin blood smears for malaria diagnosis.


METHODS
This prospective study tested 852 consecutive blood samples that underwent thick and thin smears and blinded malaria RDTs at 3 hospital laboratories during 2003-2006. Polymerase chain reaction verified positive test results and discordant results.


RESULTS
Malaria was noted in 95 (11%) of the 852 samples. The RDT had superior performance than the standard Giemsa thick blood smear (p = .003). The RDT's sensitivity for all malaria was 97% (92 of 95 samples), compared with 85% (81 of 95) for the blood smear, and the RDT had a superior NPV of 99.6%, compared with 98.2% for the blood smear (p = .001). The P. falciparum performance was excellent, with 100% rapid test sensitivity, compared with only 88% (65 of 74) by blood smear (p = .003).


CONCLUSIONS
This operational study demonstrates that the US Food and Drug Administration-approved RDT for malaria is superior to a single set of blood smears performed under routine US clinical laboratory conditions. The most valuable clinical role of the RDT is in the rapid diagnosis or the exclusion of P. falciparum malaria, which is particularly useful in outpatient settings when evaluating febrile travelers.
Stauffer
William M
WM
Department of Medicine, Division of Infectious Diseases and International Medicine, University of Minnesota, Minneapolis, Minnesota 55455, USA. stauf005@umn.edu
Cartwright
Charles P
CP
Olson
Douglas A
DA
Juni
Billie Anne
BA
Taylor
Charlotte M
CM
Bowers
Susan H
SH
Hanson
Kevan L
KL
Rosenblatt
Jon E
JE
Boulware
David R
DR
D000293:Adolescent; D000328:Adult; D000368:Aged; D000818:Animals; D000911:Antibodies, Monoclonal; D000953:Antigens, Protozoan / Q000097:blood; D002648:Child; D002675:Child, Preschool; D005260:Female; D005634:Fructose-Bisphosphate Aldolase / Q000097:blood / Q000378:metabolism; D006403:Hematologic Tests; D006801:Humans; D007223:Infant; D008288:Malaria / Q000097:blood* / Q000175:diagnosis*; D016778:Malaria, Falciparum / Q000097:blood / Q000175:diagnosis; D008297:Male; D008875:Middle Aged; D018512:Parasitemia / Q000175:diagnosis; D010961:Plasmodium / Q000201:enzymology / Q000302:isolation & purification; D016133:Polymerase Chain Reaction; D011237:Predictive Value of Tests; D011446:Prospective Studies; D015800:Protozoan Proteins / Q000097:blood; D011933:Reagent Kits, Diagnostic; D012680:Sensitivity and Specificity; D014195:Travel; D014481:United States; D014486:United States Food and Drug Administration; D055815:Young Adult
D000911:Antibodies, Monoclonal; D000953:Antigens, Protozoan; D015800:Protozoan Proteins; D011933:Reagent Kits, Diagnostic; D005634:Fructose-Bisphosphate Aldolase
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