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Updated: Oct 18, 2025
Methodology for Sputum Induction and Laboratory Processing
Published on: December 17, 2017
Performance and safety of the induced sputum procedure in young children in Malawi: a prospective study
Wongani Nyangulu1, Herbert Thole1, Angella Chikhoza1
1Paediatrics and Child Health Research Group, Malawi-Liverpool Wellcome Trust, Queen Elizabeth Central Hospital, College of Medicine, P.O. Box 30096, Chichiri, Blantyre 3, Malawi.
Insights
Induced sputum (IS) collection is safe and yields high-quality specimens in young children. This method is more sensitive than nasopharyngeal (NP) specimens for diagnosing respiratory cryptosporidiosis in hospitalized children.
Area of Science:
- Pediatric infectious diseases
- Respiratory medicine
- Diagnostic microbiology
Background:
- Collecting sputum specimens from infants and young children presents significant challenges.
- Induced sputum (IS) collection was evaluated within a study on respiratory cryptosporidiosis in Malawian children with diarrheal disease.
Purpose of the Study:
- To assess the performance and safety of induced sputum (IS) collection in infants and young children.
- To evaluate the quality and diagnostic yield of IS specimens for respiratory cryptosporidiosis.
- To compare the sensitivity of IS with nasopharyngeal (NP) specimens for Cryptosporidium detection.
Main Methods:
- Prospective study involving 162 children hospitalized with diarrheal disease.
- Collection and assessment of induced sputum (IS) and nasopharyngeal (NP) specimens.
- Analysis of sputum quality, Cryptosporidium spp. detection via PCR, and safety/adverse events.
Main Results:
- The majority of IS specimens (83%) were clear and 90% were of good quality.
- Induced sputum (IS) PCR showed higher sensitivity (29%) compared to NP PCR (12%) for detecting Cryptosporidium spp. when stool PCR was the gold standard.
- One adverse event (transient drop in oxygen saturation) was recorded, with no significant changes in other vital signs post-procedure.
Conclusions:
- Induced sputum (IS) collection is a safe and effective method for obtaining quality respiratory specimens in young children.
- IS demonstrates superior sensitivity over NP specimens for diagnosing respiratory cryptosporidiosis.
- The procedure is well-tolerated and can be safely implemented in hospitalized children presenting with diarrheal disease.
Background:
Collecting sputum specimens is a challenge in infants and young children. We assessed the performance and safety of induced sputum (IS) collection in this population, embedded in a prospective study evaluating respiratory cryptosporidiosis in Malawian children with diarrheal disease.
Methods:
We assessed the sputum quality and correlation with detection of Cryptosporidium spp. and evaluated safety and adverse events in 162 children.
Results:
Among 159 stool specimens tested, 34 (21%, 95% CI 15.0 to 28%) were positive for Cryptosporidium spp. There were 160 IS and 161 nasopharyngeal (NP) specimens collected. IS and NP specimen collection was performed for each patient. The majority of IS specimens (122/147; 83%) were clear in appearance and 132/147 (90%) were of good quality. Among the respiratory specimens tested, 10 (6.3%, 95% CI 2.5 to 10%) IS and 4 (3%, 95% CI 0 to 5%) NP were positive for Cryptosporidium spp. When stool cryptosporidium PCR was the gold standard, IS PCR sensitivity was higher (29%, 95% CI 22 to 37%) compared with NP PCR (12%, 95% CI 7 to 17%) for detection of Cryptosporidium spp. One (0.4%) adverse event occurred, consisting of a drop in oxygen saturations at the 30-min postprocedure evaluation. Consciousness level, median respiratory rate and oxygen saturations were unchanged, before or after IS.
Conclusions:
IS provides good quality specimens, is more sensitive than NP specimens for diagnosis of respiratory cryptosporidiosis, and collection can be performed safely in children hospitalized with diarrheal disease.
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