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#MayoIDCase
5 months after liver transplant, a man had recurrent fever. Blood culture: Cryptococcus neoformans. Serum cryptococcal antigen negative. What are the potential reasons for CrAg-negative culture-positive cryptococcal infection?
#MayoIDCase
5 months after liver transplant, a man had recurrent fever. Blood culture: Cryptococcus neoformans. Serum cryptococcal antigen negative. What are the potential reasons for CrAg-negative culture-positive cryptococcal infection?
2/
CrAg LFA (IMMY Diagnostics) was persistently negative despite serial dilutions.
Blood cultures on 3 consecutive days positive for C neoformans.
India ink shown (photo).
What is the most likely reason for negative CrAg?
CrAg LFA (IMMY Diagnostics) was persistently negative despite serial dilutions.
Blood cultures on 3 consecutive days positive for C neoformans.
India ink shown (photo).
What is the most likely reason for negative CrAg?
4/
CrAg may be negative if there is low antigen titer / below the limit of assay sensitivity.
In this ICH case, blood culture for 3 days are positive, suggesting a high fungal burden.
Could this CrAg (-) test be postzone effect of antigen excess ?
CrAg may be negative if there is low antigen titer / below the limit of assay sensitivity.
In this ICH case, blood culture for 3 days are positive, suggesting a high fungal burden.
Could this CrAg (-) test be postzone effect of antigen excess ?
5/
Excess antibody (prozone) or antigen (postzone) —> false-negative CrAg.
Serial dilution of sample is suggested to resolve this issue.
In this case, serial dilution resulted in persistently negative CrAg, suggesting there is likely another reason.
Excess antibody (prozone) or antigen (postzone) —> false-negative CrAg.
Serial dilution of sample is suggested to resolve this issue.
In this case, serial dilution resulted in persistently negative CrAg, suggesting there is likely another reason.
6/
MCQ Answer: Capsule-deficient Cryptococcus neoformans (see photo)
CrAg detects antigen in the fungal capsule, hence, deficient capsule may lead to false-negative CrAg.
You can read this case here: @ZYetmar @PascalisID @ETheelPhD @JClinMicro
doi.org
MCQ Answer: Capsule-deficient Cryptococcus neoformans (see photo)
CrAg detects antigen in the fungal capsule, hence, deficient capsule may lead to false-negative CrAg.
You can read this case here: @ZYetmar @PascalisID @ETheelPhD @JClinMicro
doi.org
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