Comparison of methodologies for detecting <i>Trypanosoma cruzi</i> parasites by microscopic observation of microhematocrit capillary tubes

Vera-Ku, Marina; Meza-González, Guillermo; Carlier, Yves; Truyens, Carine; Gamboa-León, Rubí

doi:10.1590/0037-8682-0505-2018

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Short Communication • Rev. Soc. Bras. Med. Trop. 52 • 2019 • https://doi.org/10.1590/0037-8682-0505-2018 copy

Comparison of methodologies for detecting Trypanosoma cruzi parasites by microscopic observation of microhematocrit capillary tubes

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

INTRODUCTION:

The microscopic examination of microhematocrit tubes (mHCT) has been proposed as the gold standard for acute and congenital Chagas disease diagnosis. We compared different mHCT methodologies detecting T. cruzi parasites in the blood.

METHODS:

The rotating method, water mount, and immersion oil methods were compared for their suitability, sensitivity, and specificity.

RESULTS:

The rotating method was easier, faster, and more sensitive than the others with 100% specificity.

CONCLUSIONS:

The rotating method is feasible for laboratory technicians with standard training in microscopic techniques and is recommended for the diagnosis of acute Chagas disease in primary health care facilities.

Keywords:
Microhematocrit test; Trypanosoma cruzi; Capillary tube test; T. cruzi diagnostic methods

Rotating	Parasites/	Total	Tubes	Tubes	False	Tubes	Tubes	False	Sensitivity	Specificity
tube	tube	tubes	with	detected	negative	without	detected	positiv
technique			parasites	positive	tubes	parasites	negative	e tubes
	10	60	30	3	27	30	30	0	78/(78+102)=0.43	180/(180+0)=1.00
	50	60	30	3	27	30	30	0
	300	60	30	3	27	30	30	0
	500	60	30	9	21	30	30	0
	1000	60	30	30	0	30	30	0
	10000	60	30	30	0	30	30	0
	Total	360	180	78	102	180	180	0
Wet mounted tube technique	10	60	30	0	30	30	30	0
	50	60	30	0	30	30	30	0
	300	60	30	0	30	29	29	1
	500	60	30	2	28	30	30	0	62(62+118)=0.34	179/(179+1)=0.99
	1000	60	30	30	0	30	30	0
	10000	60	30	30	0	30	30	0
	Total	360	180	62	118	179	179	1

	Parasites/mHCT	% of detected positive mHCT	Calculated number of positive mHCT
		(observed	using 4	using 6	using 10
		from 30 positive tubes) *	tubes	tubes	tubes
Rotating tube method	10	10.0 (+)	0.4 (-)	0.6 (-)	1.0 (+)
	50	10.0 (+)	0.4 (-)	0.6 (-)	1.0 (+)
	300	10.0 (+)	0.4 (-)	0.6 (-)	1.0 (+)
	500	30.0 (+)	1.2 (+)	1.8 (+)	3.0 (+)
	1000	100.0 (+)	4.0 (+)	6.0 (+)	10.0 (+)
	10,000	100.0 (+)	4.0 (+)	6.0 (+)	10.0 (+)
Wet mount tube method	10	0.0 (-)	0.0 (-)	0.0 (-)	0.0 (-)
	50	0.0 (-)	0.0 (-)	0.0 (-)	0.0 (-)
	300	0.0 (-)	0.0 (-)	0.0 (-)	0.0 (-)
	500	6.6 (+)	0.3 (-)	0.4 (-)	0.7 (-)
	1000	100.0 (+)	4.0 (+)	6.0 (+)	10.0 (+)
	10,000	100.0 (+)	4.0 (+)	6.0 (+)	10.0 (+)

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[1] Corresponding author: Dr. Rubí Gamboa-León. e-mail:miriamrubi2012@gmail.com