Overview
Nematodes are unsegmented roundworms. Clinical laboratory diagnosis typically identifies characteristic eggs in stool concentrates, larvae when present, or Enterobius eggs on perianal tape preparations.
Classification
| Cue | Morphology hint | Specimen |
|---|---|---|
| Ascaris | Large; thick mammillated (fertile) | Stool |
| Trichuris | Barrel; bipolar plugs | Stool |
| Hookworm group | Thin shell; early cleavage | Stool (fresh preferred) |
| Enterobius | D-shaped / flattened side | Perianal tape |
| Strongyloides | Larva morphology criteria | Stool ± special methods |
Morphologic Features
Record egg length/width, shell thickness and surface, polar plugs, and embryonation. For larvae, note length, buccal cavity relative length, and genital primordium features used in local atlases.
Laboratory Characteristics
- Most nematode eggs recovered after concentration
- Pinworm eggs uncommon in stool, use tape test
- Delayed stool may hatch hookworm eggs → larval mimics
- Adult Ascaris may be submitted as gross specimens
Reference Intervals
Detected/not detected reporting is standard. Egg quantitation, when used, follows institutional methods, verify local protocols.
Clinical and Laboratory Significance
Morphologically confirmed nematode stages support roundworm infection diagnosis. Tape-test timing and technique affect Enterobius sensitivity.
Differential Considerations
Differentiate nematode eggs from plant material and debris. Separate Strongyloides larvae from hookworm larvae using morphologic criteria and specimen history.
Comparison Tables
Stool eggs vs pinworm pathway
| Feature | Stool nematode eggs | Enterobius |
|---|---|---|
| Best specimen | Concentrated stool | Perianal tape |
| Common miss | Sparse shedding | Stool-only testing |
| Key morphology | Shell/plugs/size | Flattened side |
| Timing cue | Multiple stools if protocol | Morning before bathing often |
Classification Frameworks
Not applicable, laboratory morphologic frame, not a WHO disease list.
Laboratory Notes
- Instruct tape collection per institutional patient instructions
- Hedge hookworm-group species reporting as local convention
- No therapy language in comments
References
Authoritative textbooks, guidelines, and reviews supporting this reference entry. Verify reference intervals, critical limits, and reflex criteria against institutional protocols and current guideline editions.
Textbooks
- Forbes BA, Sahm DF, Weissfeld AS. Bailey & Scott's Diagnostic Microbiology. 15th ed. Elsevier; 2020.
- Mahon CR, Lehman DC, Manuselis G. Textbook of Diagnostic Microbiology. 6th ed. Elsevier; 2018.
- Carroll KC, Hobden JA, Miller S, et al. Jawetz, Melnick, & Adelberg's Medical Microbiology. 28th ed. McGraw-Hill; 2019.
- Murray PR, Rosenthal KS, Pfaller MA. Medical Microbiology. 9th ed. Elsevier; 2021.
CLSI and Professional Guidelines
- Clinical and Laboratory Standards Institute. Performance Standards for Antimicrobial Susceptibility Testing. CLSI document M100 (verify current edition and institutional adoption).
- Centers for Disease Control and Prevention / NIH. Biosafety in Microbiological and Biomedical Laboratories (BMBL). Current edition (verify institutional adoption).
Frequently Asked Questions
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