Aspects related to positivity for schistosomiasis: a cross-sectional study in a low prevalence area in Alagoas, Brazil, 2020

Santos, Israel Gomes de Amorim; Bezerra, Letícia Pereira; Cirilo, Tatyane Martins; Silva, Laryssa Oliveira; Machado, João Paulo Vieira; Lima, Pedro Dantas; Souza, Martha Rejane Bispo; Gomes, Sheilla da Conceição; Silva, Glória Isabel Lisboa da; Damasceno, Ivisson Abreu; Alencar, Vitória Jordana Bezerra; Carvalho, Mikaelly Maria Vieira de; Ramos, Rosália Elen Santos; Gomes, Dharliton Soares; Paz, Wandklebson Silva da; Santos Júnior, Edmilson Genuíno; Alves, Luiz Carlos; Brayner, Fábio André

doi:10.1590/S1679-49742021000200005

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ORIGINAL ARTICLE • Epidemiol. Serv. Saúde 30 (2) • 2021 • https://doi.org/10.1590/S1679-49742021000200005 linkcopy

Aspects related to positivity for schistosomiasis: a cross-sectional study in a low prevalence area in Alagoas, Brazil, 2020^*

Authorship SCIMAGO INSTITUTIONS RANKINGS

Objective: To analyze aspects related to schistosomiasis positivity in an area of low prevalence in Brazil.

Methods: This was a cross-sectional study, carried out in the first half of 2020, where we analyzed the proportion of positivity, according to the number of Kato-Katz slides, the diagnostic performance of the test and positivity estimates based on data from the Schistosomiasis Surveillance and Control Program Information System (SISPCE).

Results: 2,088 slides from 348 individuals were analyzed, with proportion of positivity of 11.8%, 26.7% and 31.0% for 1, 4 and 6 slides analyzed, respectively. There was excellent agreement (Kappa = 0.91) between the readings of 4 and 6 slides. The SISPCE data was estimated to be underreported by up to 2.1 times.

Conclusion: Increasing the number of slides increased Kato-Katz positivity, which can contribute to maximizing the control of the disease as a Public Health problem.

Keywords:
Neglected Diseases; Cross-Sectional Studies; Sensitivity and Specificity; Public Health; Schistosomiasis Mansoni; Parasitic Diseases

Samples	Slide 1 + Slide 2		Slide 1		Slide 2		p-value^a
Samples	N	Positivity^b	N	Positivity^b	N	Positivity^b	p-value^a
Sample 1
Positive
Yes	64	18.4	51	14.6	45	12.9	p<0.001
No	284		297		303
Total	348		348		348
Sample 2
Positive
Yes	69	19.8	57	16.4	41	11.8	p<0.001
No	279		291		307
Total	348		348		348
Sample 3
Positive
Yes	68	19.5	50	14.4	43	12.3	p<0.001
No	280		298		305
Total	348		348		348

Sample	Schistosomal Infection
Sample	Light^a (average eggs)^b	Moderate^a (average eggs)^b	Heavyᵃ (average eggs)
1^st sample / 2 slides	58 (31.6)	4 (196.5)	2 (684.0)
2^nd sample / 2 slides	62 (29.3)	6 (206.0)	1 (528.0)
3^rd sample / 2 slides	58 (37.8)	10 (229.8)	1 (420.0)
2 samples / 4 slides	86 (30.2)	6 (209.0)	1 (552.0)
3 samples / 6 slides	97 (32.3)	9 (193.8)	1 (406.0)

KK^a	6 slides analyzed				Positivity		Relationship between positivity rates
	Co-positivity	Co-negativity	McNemar p-value	Kappa^b	Reference^c	6 slides
	Co-positivity	Co-negativity	McNemar p-value	Kappa^b	Reference^c	6 slides
1	48.0%	100.0%	53.02 p<0.001	0.56	14.6%	31.0%	2.1
2	60.0%	100.0%	40.02 p<0.001	0.67	18.4%	31.0%	1.7
4	88.7%	100.0%	1.00 p>0.05	0.91	26.7%	31.0%	1.2

Locations	Average positivity rate (%) SISPCE Data 2010-2016	Average positivity rate (%) Study Data^a
Locations	Average positivity rate (%) SISPCE Data 2010-2016	1	2	3	4	5	6	7 ^a
Alto do Cruzeiro	23.3	50^b	50^b	0	0	0	50^b	50^b
Antunica de Baixo	17.1	0	40^b	20^b	20^b	20^b	0	40^b
Antunica de Cima	3.2	8^b	8^b	8^b	8^b	38^b	15^b	38^b
Barro Preto	11.6	20^b	30^b	10	0	20^b	0	50^b
Cavaco	11.4	0	0	10	0	30^b	10	40^b
Funil	20.6	0	0	8	8	8	0	8
Lagoa da Pedra	12.1	13^b	13^b	13^b	0	0	0	25^b
Lagoa do Mato	13.4	9	9	27^b	18^b	18^b	18^b	36^b
Mata Limpa	10.0	4	0	4	8	0	4	16^b
Olho d’Água da Canoa	15.4	28^b	33^b	22^b	22^b	17^b	11	44^b
Pau d’Arco	40.0	6	6	0	6	0	0	6
Zona Urbana	9.4	22^b	17^b	27^b	17^b	20^b	20^b	42^b

Locations	Average Recorded Positivity^a	Average Estimated Positivityᵃ
Alexandre	6.3	13.2
Alto do Cruzeiro	23.3	48.9
Antunica de Baixo	17.1	35.9
Antunica de Cima	3.2	6.7
Barro Preto	11.6	24.3
Barro Vermelho	0.9	1.9
Boa Vista I	3.0	6.4
Campestrinho	34.1	71.6
Capim	11.1	23.2
Cavaco	11.4	23.9
Chã do Pau d’Arco	14.8	31.1
Folha Miúda de Baixo	2.1	4.4
Funil	20.6	43.3
Jenipapo	8.5	17.8
Jurema	9.7	20.3
Lagoa da Braúna	6.2	13.1
Lagoa da Canoa	9.4	19.8
Lagoa do Mato	13.4	28.2
Lagoa da Pedra	12.1	25.5
Lagoa das Varas	10.7	22.5
Lagoa Grande	8.0	16.8
Lagoa Queimada	11.3	23.8
Mata Limpa	10.1	21.1
Olho d'Água da Canoa	15.4	32.4
Padre Cícero	6.7	14.0
Pau d'Arco	39.9	84.0
Pintada	5.0	10.6
Riacho Grande	20.0	42.0
Riacho Fundo	11.3	23.7
Riacho Fundo de Cima	20.0	42.0
Santa Clara	26.1	54.8
São José III	8.0	16.9
Sizília	16.9	35.5

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[TFN6] a) Chi-square test of independence: comparison of the proportions between the sum of the two slides and the result of the reading of each slide; b) Proportion of positivity.

Aspects related to positivity for schistosomiasis: a cross-sectional study in a low prevalence area in Alagoas, Brazil, 2020*

Aspects related to positivity for schistosomiasis: a cross-sectional study in a low prevalence area in Alagoas, Brazil, 2020^*