Correspondence

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  • 1 Infectious Diseases Department Naval Medical Research Institute, Bethesda, Maryland 20814
  • 2 Department of Preventive Medicine and Biometrics Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814

Dr. Pang states that our study on the use of a DNA probe to diagnose P. falciparum malaria failed to demonstrate “in humans sensitivity of the probe for low parasitemias (< 10 parasites per 200 WBC).” The 25 patient samples analyzed in this study included 4 with P. falciparum parasitemias ≤ 10 parasites/200 WBCs; all 4 were correctly diagnosed by the probe following 18 hr film exposure (see Table 2 of Ref. 1). Furthermore, assuming an average of 7,000 WBC/µl and 5 × 106 RBC/µl, 10 parasites/200 WBC and 5 parasites/200 WBC correspond approximately to parasitemias of 0.007% and 0.0035%, respectively. Our lowest level of detection in the endemic patient population we studied was 2 parasites/200 WBC, or a 0.0014% parasitemia. We, therefore, have no reason to believe our technique will not be sensitive in the range of parasitemias reported by Dr. Pang from the Thai-Burmese border.

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