How Long Can Stool Samples Be Fixed for an Accurate Diagnosis of Soil-Transmitted Helminth Infection Using Mini-FLOTAC?

Beatrice Barda, Marco Albonico, Davide Ianniello, Shaali M. Ame, Jennifer Keiser, Benjamin Speich, Laura Rinaldi, Giuseppe Cringoli, Roberto Burioni, Antonio Montresor, Jürg Utzinger

Research output: Contribution to journalArticle

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Abstract

Kato-Katz is a widely used method for the diagnosis of soil-transmitted helminth infection. Fecal samples cannot be preserved, and hence, should be processed on the day of collection and examined under a microscope within 60 min of slide preparation. Mini-FLOTAC is a technique that allows examining fixed fecal samples. We assessed the performance of Mini-FLOTAC using formalin-fixed stool samples compared to Kato-Katz and determined the dynamics of prevalence and intensity estimates of soil-transmitted helminth infection over a 31-day time period. The study was carried out in late 2013 on Pemba Island, Tanzania. Forty-one children were enrolled and stool samples were subjected on the day of collection to a single Kato-Katz thick smear and Mini-FLOTAC examination; 12 aliquots of stool were fixed in 5% formalin and subsequently examined by Mini-FLOTAC up to 31 days after collection. The combined results from Kato-Katz and Mini-FLOTAC revealed that 100% of children were positive for Trichuris trichiura, 85% for Ascaris lumbricoides, and 54% for hookworm. Kato-Katz and Mini-FLOTAC techniques found similar prevalence estimates for A. lumbricoides (85% versus 76%), T. trichiura (98% versus 100%), and hookworm (42% versus 51%). The mean eggs per gram of stool (EPG) according to Kato-Katz and Mini-FLOTAC was 12,075 and 11,679 for A. lumbricoides, 1,074 and 1,592 for T. trichiura, and 255 and 220 for hookworm, respectively. The mean EPG from day 1 to 31 of fixation was stable for A. lumbricoides and T. trichiura, but gradually declined for hookworm, starting at day 15. The findings of our study suggest that for a qualitative diagnosis of soil-transmitted helminth infection, stool samples can be fixed in 5% formalin for at least 30 days. However, for an accurate quantitative diagnosis of hookworm, we suggest a limit of 15 days of preservation. Our results have direct implication for integrating soil-transmitted helminthiasis into transmission assessment surveys for lymphatic filariasis.

Original languageEnglish
Article numbere0003698
JournalPLoS Neglected Tropical Diseases
Volume9
Issue number4
DOIs
Publication statusPublished - Apr 7 2015

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Ancylostomatoidea
Helminths
Ascaris lumbricoides
Trichuris
Soil
Formaldehyde
Infection
Eggs
Indian Ocean Islands
Filarial Elephantiasis
Helminthiasis
Tanzania
Islands

ASJC Scopus subject areas

  • Infectious Diseases
  • Public Health, Environmental and Occupational Health
  • Pharmacology, Toxicology and Pharmaceutics(all)

Cite this

How Long Can Stool Samples Be Fixed for an Accurate Diagnosis of Soil-Transmitted Helminth Infection Using Mini-FLOTAC? / Barda, Beatrice; Albonico, Marco; Ianniello, Davide; Ame, Shaali M.; Keiser, Jennifer; Speich, Benjamin; Rinaldi, Laura; Cringoli, Giuseppe; Burioni, Roberto; Montresor, Antonio; Utzinger, Jürg.

In: PLoS Neglected Tropical Diseases, Vol. 9, No. 4, e0003698, 07.04.2015.

Research output: Contribution to journalArticle

Barda, B, Albonico, M, Ianniello, D, Ame, SM, Keiser, J, Speich, B, Rinaldi, L, Cringoli, G, Burioni, R, Montresor, A & Utzinger, J 2015, 'How Long Can Stool Samples Be Fixed for an Accurate Diagnosis of Soil-Transmitted Helminth Infection Using Mini-FLOTAC?', PLoS Neglected Tropical Diseases, vol. 9, no. 4, e0003698. https://doi.org/10.1371/journal.pntd.0003698
Barda, Beatrice ; Albonico, Marco ; Ianniello, Davide ; Ame, Shaali M. ; Keiser, Jennifer ; Speich, Benjamin ; Rinaldi, Laura ; Cringoli, Giuseppe ; Burioni, Roberto ; Montresor, Antonio ; Utzinger, Jürg. / How Long Can Stool Samples Be Fixed for an Accurate Diagnosis of Soil-Transmitted Helminth Infection Using Mini-FLOTAC?. In: PLoS Neglected Tropical Diseases. 2015 ; Vol. 9, No. 4.
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