diagnosis

Last edited 09/2018

diagnosis

A positive diagnosis of Cryptosporidiosis can be achieved through demonstrating the presence of Cryptosporidium oocysts or Cryptosporidium antigen in a sample.

  • Cryptosporidiumoocysts in the stool can be detected using acid-fast or auramine-phenol staining

  • antigen-detection assays are more sensitive and can be used if oocysts are not detected in stool specimens and if suspicion is high for cryptosporidiosis or limited oocyst excretion
    • genotyping and subtyping tools are being increasingly used to differentiate Cryptosporidiumspecies in outbreak investigations and infection/contamination source tracking (1,2,3)

Oocyst excretion can be intermittent; therefore, the parasite may not be detected in every stool sample, and stool specimens collected on 3 consecutive days should be examined before considering test results to be negative (2).

Types of specimens used to examine for Cryptosporidium include the following:

  • stool
    • most commonly examined specimen
    • useful in any patient with community acquired or unexplained diarrhoea
  • jejuna +/- gastric biopsy
    • persistent idiopathic gastrointestinal symptoms in high risk groups
  • bile from endoscopic retrograde cholangio-pancreatography
    • if symptoms of cholangitis in high risk groups
  • sputum/ bronchoalveolar lavage
    • high risk patients with profound immunosuppression and unexplained respiratory symptoms
  • antral washout
    • high risk patients with profound immunosuppression and unexplained sinusitis

Note:

  • clinicians should be familiar with local laboratory practices and should specifically request Cryptosporidium testing on the request form (3)

Reference: