Comparison of PCR and microscopy for the detection of asymptomatic malaria in a Plasmodium falciparum/vivax endemic area in Thailand

Table 1 Comparison of PCR and expert laboratory microscopy for active malaria surveillance.

Expert microscopy resμlt	No. of samples with the following result by PCR (% of total in row)
Expert microscopy resμlt	P. falciparum	P. vivax	P. malariae	P. ovale	Mixed	Negative	Total
P. falciparum	102 (38.4%)	13 (4.9%)	0 (0.0%)	0 (0.0%)	7 (2.7%)	143 (54.0%) ^a	265
P. vivax	4 (1.0%)	131 (33.9%)	1 (0.3%)	0 (0.0%)	8 (2.1%)	242 (62.7%) ^b	386
P. malariae	0 (0.0%)	0 (0.0%)	8 (80.0%)	0 (0.0%)	0 (0.0%)	2 (20.0%)	10
Mixed	3 (75.0%)	0 (0.0%)	0 (0.0%)	0 (0.0%)	1 (25.0%)	0 (0.0%)	4
Negative	70 (0.9%)	214 (2.7%)	7 (0.1%)	2 (<0.1%)	18 (0.2%)	7,614 (96.1%)	7,925
Total	179 (2.1%)	358 (4.2%)	16 (0.2%)	2 (<0.1%)	34 (0.40%) ^c	8,001 (93.1%)	8,590

^a 98% (140/143) of microscopy-positive P. falciparum samples that were PCR negative had <250 parasites/μl.
^b 99% (239/242) of microscopy-positive P. vivax samples that were PCR negative had <250 parasites/μl.
^c Includes the following mixed infections: 28 P. falciparum/P. vivax, 3 P. vivax/P. ovale, 2 P. vivax/P. malariae and 1 P. falciparum/P. malariae.

ISSN: 1475-2875