Skip to main content Accessibility help

Parasitological versus molecular diagnosis of strongyloidiasis in serial stool samples: how many?

  • E. Dacal (a1), J.M. Saugar (a1), T. Soler (a1), J.M. Azcárate (a1), M.S. Jiménez (a1), F.J. Merino (a2) and E. Rodríguez (a1)...


Strongyloidiasis is usually an asymptomatic disease in immunocompetent patients, caused by Strongyloides stercoralis. However, in immunocompromised patients it can produce a severe clinical profile. Therefore, a correct diagnosis is necessary in these cases and in those chronic asymptomatic patients. The low sensitivity of classical parasitological techniques requires the analysis of multiple serial stool samples. Molecular diagnostic techniques represent an improvement in the detection of the parasite. The objective of this study was to evaluate the minimum number of samples necessary to achieve maximum sensitivity by real-time polymerase chain reaction (PCR). A total of 116 stool samples from 39 patients were analysed by direct microscopic observation, agar culture, Harada–Mori and real-time PCR, in one, two, three and four or more consecutive samples. After two serial samples, 6 out of 39 patients were positive by parasitological and molecular techniques, while 16 of them were real-time PCR positive, and all the patients detected by parasitology were also detected by the molecular technique, reaching 100.00% sensitivity versus 83.00% when analysing a single sample. These data also reflect apparently low specificity (51.52%) and positive predictive value (PPV) (27.27 %) values, due to the high number of cases detected by real-time PCR and not by parasitological techniques. These cases were confirmed as true positives when analysing three, four or more samples from the same patient. In conclusion, the application of molecular techniques decreases the number of serial stool samples necessary to give a diagnosis with the maximum sensitivity.


Corresponding author


Hide All
Becker, S.L., Piraisoody, N., Kramme, S., Marti, H., Silué, K.D., Panning, M., Nickel, B., Kern, W.V., Herrmann, M., Hatz, C.F., N'Goran, E.K., Utzinger, J. & von Müller, L. (2015) Real-time PCR for detection of Strongyloides stercoralis in human stool samples from Côte d'Ivoire: diagnostic accuracy, inter-laboratory comparison and patterns of hookworm co-infection. Acta Tropica 150, 210217.
Buonfrate, D., Formenti, F., Perandin, F. & Bisoffi, Z. (2015) Novel approaches to the diagnosis of Strongyloides stercoralis infection. Clinical Microbiology and Infection 21, 543552.
Cañavate, C., Cuadros, J., Martínez Ruiz, R. & Martin-Rabadán, P. (2009) El laboratorio de microbiología ante las enfermedades parasitarias importadas. pp. 135 in Cercenado, E. & Cantón, R. (Eds) Procedimientos en Microbiología Clínica. Madrid, Spain, Sociedad Española de Enfermedades Infecciosas y Microbiología Clínica (SEIMC).
Conraths, F.J. & Schares, G. (2006) Validation of molecular-diagnostic techniques in the parasitological laboratory. Veterinary Parasitology 136, 9198.
Hulsen, T., de Vlieg, J. & Alkema, W. (2008) BioVenn – a web application for the comparison and visualization of biological lists using area-proportional Venn diagrams. BMC Genomics 9, 488.
Janwan, P., Intapan, P.M., Thanchomnang, T., Lulitanond, V., Anamnart, W. & Maleewong, W. (2011) Rapid detection of Opisthorchis viverrini and Strongyloides stercoralis in human fecal samples using a duplex real-time PCR and melting curve analysis. Parasitology Research 109, 15931601.
Knopp, S., Mgeni, A.F., Khamis, I.S., Steinmann, P., Stothard, J.R., Rollinson, D., Marti, H. & Utzinger, J. (2008) Diagnosis of soil-transmitted helminths in the era of preventive chemotherapy: effect of multiple stool sampling and use of different diagnostic techniques. PLoS Neglected Tropical Diseases 2, e331.
Llewellyn, S., Inpankaew, T., Nery, S.V., Gray, D.J., Verweij, J.J., Clements, A.C., Gomes, S.J., Traub, R. & McCarthy, J.S. (2016) Application of a Multiplex Quantitative PCR to assess prevalence and intensity of intestinal parasite infections in a controlled clinical trial. PLoS Neglected Tropical Diseases 10, e0004380.
Marcos, L.A., Terashima, A., Dupont, H.L. & Gotuzzo, E. (2008) Strongyloides hyperinfection syndrome: an emerging global infectious disease. Transactions of the Royal Society of Tropical Medicine and Hygiene 102, 314318.
Mejia, R., Vicuña, Y., Broncano, N., Sandoval, C., Vaca, M., Chico, M., Cooper, P.J. & Nutman, T.B. (2013) A novel, multi-parallel, real-time polymerase chain reaction approach for eight gastrointestinal parasites provides improved diagnostic capabilities to resource-limited at-risk populations. American Journal of Tropical Medicine and Hygiene 88, 10411047.
Moghaddassani, H., Mirhendi, H., Hosseini, M., Rokni, M., Mowlavi, G. & Kia, E. (2011) Molecular diagnosis of Strongyloides stercoralis infection by PCR detection of specific DNA in human stool samples. Iran Journal of Parasitology 6, 2330.
Montes, M., Sawhney, C. & Barros, N. (2010) Strongyloides stercoralis: there but not seen. Current Opinion Infectious Diseases 23, 500504.
Nielsen, P.B. & Mojon, M. (1987) Improved diagnosis of Strongyloides stercoralis by seven consecutive stool specimens. Zentralblatt für Bakteriologie Mikrobiologie und Hygiene A 263, 616618.
Olsen, A., van Lieshout, L., Marti, H., Polderman, T., Polman, K., Steinmann, P., Stothard, R., Thybo, S., Verweij, J.J. & Magnussen, P. (2009) Strongyloidiasis the most neglected of the neglected tropical diseases? Transactions of the Royal Society of Tropical Medicine and Hygiene 103, 967972.
Repetto, S.A., Ruybal, P., Solana, M.E., López, C., Berini, C.A., Alba Soto, C.D. & Cappa, S.M. (2016) Comparison between PCR and larvae visualization methods for diagnosis of Strongyloides stercoralis out of endemic area: a proposed algorithm. Acta Tropica 157, 169177.
Requena-Méndez, A., Chiodini, P., Bisoffi, Z., Buonfrate, D., Gotuzzo, E. & Muñoz, J. (2013) The laboratory diagnosis and follow up of strongyloidiasis: a systematic review. PLoS Neglected Tropical Diseases 7, e2002
Saugar, J.M., Merino, F.J., Martín-Rabadán, P., Fernández-Soto, P., Ortega, S., Gárate, T. & Rodríguez, E. (2015) Application of real-time PCR for the detection of Strongyloides spp. in clinical samples in a reference center in Spain. Acta Tropica 42, 2025.
Schär, F., Trostdorf, U., Giardina, F., Khieu, V., Muth, S., Marti, H., Vounatsou, P. & Odermatt, P. (2013a) Strongyloides stercoralis: global distribution and risk factors. PLoS Neglected Tropical Diseases 7, e2288.
Schär, F.I., Odermatt, P., Khieu, V., Panning, M., Duong, S., Muth, S., Marti, H. & Kramme, S. (2013b) Evaluation of real-time PCR for Strongyloides stercoralis and hookworm as diagnostic tool in asymptomatic schoolchildren in Cambodia. Acta Tropica 126, 8992.
Siddiqui, A.A. & Berk, S.L. (2001) Diagnosis of Strongyloides stercoralis infection. Clinical Infectious Diseases 33, 10401047.
Sitta, R.B., Malta, F.M., Pinho, J.R., Chieffi, P.P., Gryschek, R.C. & Paula, F.M. (2014) Conventional PCR for molecular diagnosis of human strongyloidiasis. Parasitology 141, 716721.
Sultana, Y., Jeoffreys, N., Watts, M.R., Gilbert, G.L. & Lee, R. (2013) Real-time polymerase chain reaction for detection of Strongyloides stercoralis in stool. American Journal of Tropical Medicine and Hygiene 88, 10481051.
Verweij, J.J. (2014) Application of PCR-based methods for diagnosis of intestinal parasitic infections in the clinical laboratory. Parasitology 141, 18631872.
Verweij, J.J., Canales, M., Polman, K., Ziem, J., Brienen, E.A., Polderman, A.M. & van Lieshout, L. (2009) Molecular diagnosis of Strongyloides stercoralis in faecal samples using real-time PCR. Transactions of the Royal Society of Tropical Medicine and Hygiene 103, 342346.

Parasitological versus molecular diagnosis of strongyloidiasis in serial stool samples: how many?

  • E. Dacal (a1), J.M. Saugar (a1), T. Soler (a1), J.M. Azcárate (a1), M.S. Jiménez (a1), F.J. Merino (a2) and E. Rodríguez (a1)...


Altmetric attention score

Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed