Letters to the Editor

Rapid ‘Dipstick’ Assays for the Detection of Malaria



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Am Fam Physician. 2000 Mar 15;61(6):1640-1643.

to the editor: I enjoyed the recent article “Case Studies in International Travelers,”1  in which Dr. Kitchen discussed several clinical vignettes of illnesses, including malaria, in travelers returning to the United States. Microscopy of serial blood smears to detect the presence of the malaria parasites (plasmodium species) continues to be the “gold standard” for clinical diagnosis because it allows estimation of parasitemia, distinction between parasite growth stages and identification of the four different plasmodium species of malaria. However, the article did not address the recent advances in rapid “dipstick” assays to detect malaria. Several commercially available immunochromatographic antigen detection assays are available (see the accompanying table). These assays have been used in various clinical settings in North America and endemic regions.

Rapid “Dipstick” Blood Tests for Detection of Malaria

Assay (company; contact address) Plasmodium species identified Parasite antigen detected Sensitivity (%) Specificity (%)

OptiMAL4,5 Flow Inc., Portland, OR Web site: http://www.malariatest.com

P. falciparum

Parasite lactate dehydrogenase

88-91 (P.f)

92-99 (P.f)

P. vivax

94 (P.v)

100 (P.v)

ICT Malaria P.f/P.v6 AMRAD ICT, Sydney, NSW, Australia Web site: http://www.amrad.com.au

P. falciparum

HRP-2

95 (P.f)

89 (P.f)

P. vivax

75 (P.v)

95 (P.v)

PATH Falciparum Malaria IC Strip2 Quorum Diagnostics, Vancouver, Canada E-mail: info@path.org

P. falciparum

HRP-2

96

99

Parasight-F 3 Becton Dickinson Tropical Diagnostics, Sparks, MD Web site: http://www.bdms.com

P. falciparum

HRP-2

94

95

ICT Malaria P.f3 AMRAD ICT, Sydney, NSW, Australia Web site: http://www.amrad.com.au

P. falciparum

HRP-2

90

97


P.f = Plasmodium falciparum; P.v = Plasmodium vivax; HRP-2 = histidine-rich protein 2.

Information from references 2, 3, 4, 5 and 6.

Rapid “Dipstick” Blood Tests for Detection of Malaria

View Table

Rapid “Dipstick” Blood Tests for Detection of Malaria

Assay (company; contact address) Plasmodium species identified Parasite antigen detected Sensitivity (%) Specificity (%)

OptiMAL4,5 Flow Inc., Portland, OR Web site: http://www.malariatest.com

P. falciparum

Parasite lactate dehydrogenase

88-91 (P.f)

92-99 (P.f)

P. vivax

94 (P.v)

100 (P.v)

ICT Malaria P.f/P.v6 AMRAD ICT, Sydney, NSW, Australia Web site: http://www.amrad.com.au

P. falciparum

HRP-2

95 (P.f)

89 (P.f)

P. vivax

75 (P.v)

95 (P.v)

PATH Falciparum Malaria IC Strip2 Quorum Diagnostics, Vancouver, Canada E-mail: info@path.org

P. falciparum

HRP-2

96

99

Parasight-F 3 Becton Dickinson Tropical Diagnostics, Sparks, MD Web site: http://www.bdms.com

P. falciparum

HRP-2

94

95

ICT Malaria P.f3 AMRAD ICT, Sydney, NSW, Australia Web site: http://www.amrad.com.au

P. falciparum

HRP-2

90

97


P.f = Plasmodium falciparum; P.v = Plasmodium vivax; HRP-2 = histidine-rich protein 2.

Information from references 2, 3, 4, 5 and 6.

The older “dipstick” tests (Parasight-F, ICT Malaria P.f and PATH Falciparum Malaria IC Strip) detect only Plasmodium falciparum infection. All three assays detect histidine-rich protein 2, an antigen expressed only by P. falciparum trophozoites.2,3 However, the two newer tests (the OptiMAL assay, and the ICT Malaria P.f/P.v assay) have the advantage of detecting infection with P. falciparum or Plasmodium vivax. The OptiMAL assay detects parasite lactate dehydrogenase (pLDH) and can distinguish between P. falciparum and P. vivax because of antigenic differences between their pLDH isoenzymes.4,5 Because only live parasites produce pLDH, this test can be of clinical relevance because it distinguishes between living (current infection) and dead parasites (recently treated infection). The ICT Malaria P.f/P.v test detects histidine-rich protein 2 found only in P. falciparum and panmalarial antigens found in P. vivax, again, allowing the two species to be differentiated.6

Although some of these assays are relatively expensive and are awaiting final labeling approval from the U.S. Food and Drug Administration, they can provide excellent diagnostic aids for family physicians caring for immigrants or travelers who have recently returned from malarious areas, as well as for physicians providing health care to persons in developing countries—especially if a trained microscopist is not readily available.

REFERENCES

1. Kitchen LW. Case studies in international travelers. Am Fam Physician. 1999;60:471–4.

2. Mills CD, Burgess DC, Taylor HJ, Kain KC. Evaluation of a rapid and inexpensive dipstick assay for the diagnosis of Plasmodium falciparum malaria. Bull World Health Organ. 1999;77:553–9.

3. Pieroni P, Mills CD, Ohrt C, Harrington MA, Kain KC. Comparison of the ParaSight-F test and the ICT Malaria Pf test with the polymerase chain reaction for the diagnosis of Plasmodium falciparum malaria in travellers. Trans R Soc Trop Med Hyg. 1998;92:166–9.

4. Palmer CJ, Lindo JF, Klaskala WI, Quesada JA, Kaminsky R, Baum MK, et al. Evaluation of the OptiMAL test for rapid diagnosis of Plasmodium vivax and Plasmodium falciparum malaria. J Clin Microbiol. 1998;36:203–6.

5. Cooke AH, Chiodini PL, Doherty T, Moody AH, Ries J, Pinder M. Comparison of a parasite lactate dehydrogenase-based immunochromatographic antigen detection assay (OptiMAL) with microscopy for the detection of malaria parasites in human blood samples. Am J Trop Med Hyg. 1999;60:173–6.

6. Tjitra E, Suprianto S, Dyer M, Currie BJ, Anstey NM. Field evaluation of the ICT malaria P.f/P.v immunochromatographic test for detection of Plasmodium falciparum and Plasmodium vivax in patients with a presumptive clinical diagnosis of malaria in eastern Indonesia. J Clin Microbiol. 1999;37:2412–7.

in reply : Dr. Thompson's points are well taken. At the time I wrote my article,1 I was unaware of the newer multispecies “dipstick” malaria-detection tests he describes.

REFERENCE

1. Kitchen LW. Case studies in international travelers. Am Fam Physician. 1999;60:471–4.

Send letters to Kenneth W. Lin, MD, MPH, Associate Deputy Editor for AFP Online, e-mail: afplet@aafp.org, or 11400 Tomahawk Creek Pkwy., Leawood, KS 66211-2680.

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