Malaria Testing Changes

Effective Monday, July 11, 2011, all specimens sent for malarial examination will be initially screened with a malarial antigen assay.  This assay can rapidly identify patients infected with Plasmodium falciparum at parasitemia levels of 0.1% or higher, and it can also identify cases of malaria caused by other species (e.g. P. vivax, etc.).  However, it cannot specifically classify Plasmodium species other than P. falciparum.  The assay has a high negative predictive value for malaria.  To provide optimum sensitivity and specificity, all specimens will continue to be Giemsa stained and examined microscopically by a pathologist, regardless of the antigen result.

Malaria antigen will be tested 24 hours a day, 7 days a week, including holidays.  Giemsa smears will be performed on all specimens from 0700-1900, 7 days a week, including holidays.  Antigen results will be available within one hour of specimen arrival, 24 hours a day.  A positive malaria antigen result will be considered a critical value and the ordering physician will be contacted by the laboratory.  Preliminary thin smear results will be available within 90 minutes of specimen arrival if the specimen arrives between 0700-1900 or by 0930 if specimen arrives after hours.  Thick smear results and final reports will follow within 24 hours. 

Label and draw an EDTA whole blood tube and submit STAT to the Microbiology Lab 0700-2300 or to the Core Lab 2300-0700.  If any delay in delivery to the laboratory is anticipated, refrigerate the blood sample to prevent malaria antigen degradation.

One negative specimen does not rule out malaria.  If clinical suspicion for malaria remains after one negative sample, additional specimens should be submitted at 12 hour intervals for the subsequent 36 hour period, preferably timed with fever spikes.  Place a note in the order if a parasite other than malaria is suspected (e.g. trypanosomes).

EPIC Code/Test Name:  LAB2294/Microbiology: Giemsa Smear (R/O Malaria or Fungi)

Questions concerning malarial/blood parasite testing can be directed to Stacey Klutts, MD, PhD (ext. 6-2990) or Dan Diekema, MD (ext. 4-5626).