PCR reveals significantly higher rates of Trypanosoma cruzi infection than microscopy in the Chagas vector, Triatoma infestans : High rates found in Chuquisaca, Bolivia

BMC Infectious Diseases

Table 2 Comparison of PCR and Microscopy for T. cruzi detection in T. infestans by developmental stage* in Chuquisaca, Bolivia

Stage	PCR %	Microscopy %	Sample size	P-value**	Discrepancy %	Kappa	s.e.
N1	80.00	60.00	10	0.05	20.00	0.54	0.26
N2	80.00	48.00	25	0.02	32.00	0.37	0.14
N3	82.61	47.83	23	0.03	34.78	0.32	0.14
N4	100.00	50.00	6	0.39	50.00	NA	NA
N5	80.00	70.00	30	<0.0001	10.00	0.74	0.14
A	79.55	56.82	40	0.0002	24.44	0.38	0.13
Total	81.16	56.52	138	<0.0001	24.64	0.43	0.07
Sensitivity	100.00	69.64		<0.0001

* Serrano and Carbajal not included in the analysis
N1–N5 = First to fifth nymphal stages; A = Adults; PCR = Polymerase Chain Reaction;
Discrepancy = PCR positive and Microscopy negative; NA = Non applicable
** P-value = Probability that the differences in infection rates between techniques is due to chance