- Parasite Classification |
- Parasite, Body Site |
- Stool Testing Order Recommendations |
- STAT Testing |
- Fecal Fixatives |
- Stool Collection Options |
- Report Comments |
- Tips for Fecal ImmunoAssay |
- Malaria (5 Species) |
- Malaria (5 Species) Images |
- Rapid Malaria Testing |
- Malaria Parasitemia Method |
- Malaria Parasitemia Interpretation |
Parasitemia determined from conventional light microscopy:
clinical correlation AND INTERPRETATION
Parasitemia (%) |
No. of Parasites/µl |
Clinical Correlationa |
0.0001-0.0004 |
5-20 |
Number of organisms required for positive thick film (sensitivity) |
0.002 |
100 |
Patients may be symptomatic below this level, particularly if they are immunologically naïve (no prior exposure to malaria) (Example: travelers) |
0.02 |
1,000 |
Level often seen in travelers (immunologically naïve) – results may also be lower than this |
0.1 |
5,000 |
BinaxNOW® rapid lateral flow method (dipstick) (>5000 = 99.7% sensitivity for P. falciparum) |
0.2 |
10,000 |
Level above which immune patients will exhibit symptoms |
2 |
100,000 |
Maximum parasitemia of P. vivax and P. ovale (which infect young RBCs only) |
2-5 |
100,000 – 250,000 |
Hyperparasitemia, severe malariab; increased mortality |
10 |
500,000 |
Exchange transfusion may be considered; high mortality |
The BinaxNOW® malaria test (Inverness Medical, Scarborough, ME) is FDA approved. The BinaxNOW® Malaria Test detects antigen from both viable and non-viable malaria organisms, including gametocytes and sequestered P. falciparum parasites. Test performance depends on antigen load in the specimen and may not directly correlate with microscopy performed on the same specimen. Samples with positive rheumatoid factor titers may produce false positive results. Analytical reactivity testing demonstrates that the pan malarial test line on the BinaxNOW® test is capable of detecting all five malaria species. However, during clinical trials, insufficient data was generated to support clinical performance claims for the detection of P. malariae, P. ovale, or P. knowlesi. Clinical performance claims for this test are made for P. falciparum and P. vivax detection only. The test is not intended for use in screening asymptomatic populations. (BinaxNOW® malaria test package insert (Inverness Medical, Scarborough, ME). The BinaxNOW Positive Malaria Control, as well as the BinaxNOW® Malaria test, is available commercially (Inverness Medical, Scarborough, ME).
World Health Organization criteria for severe malaria are parasitemia of >10,000/µl and severe anemia (hemoglobin, <5 g/liter). Prognosis is poor if >20% of parasites are pigment-containing trophozoites and schizonts and/or if >5% of neutrophils contain visible pigment.