Diagnosis

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:

• (1) European Centre for Disease prevention Control (ECDC) 2012. Rapid risk assessment. Increased Cryptosporidium infections in the Netherlands, United Kingdom and Germany in 2012
• (2) Siberry GK et al. Guidelines for the prevention and treatment of opportunistic infections in HIV-exposed and HIV-infected children: recommendations from the National Institutes of Health, Centers for Disease Control and Prevention, the HIV Medicine Association of the Infectious Diseases Society of America, the Pediatric Infectious Diseases Society, and the American Academy of Pediatrics. Pediatr Infect Dis J. 2013;32 Suppl 2:i-KK4
• (3) Davies AP, Chalmers RM. Cryptosporidiosis. BMJ. 2009;339:b4168.