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Lab Manual for UCSF Clinical Laboratories

Lab Manual for SFGH

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Clinical Laboratories Frequently Asked Questions (FAQs)

  1. Why can't I order a full fungal culture on CSF?
  2. Which common hematology tests require quick delivery to the clinical labs?

1. Why can't I order a full fungal culture on CSF?

Fungal cultures are held for weeks to detect slow growing Dermatophytes, which would be a very rare finding in CSF. CSF is tested for cryptococcal antigen and can be cultured for Cryptococcus. The antigen test is available from 0800 to 2230 hours. The Cryptococcus culture system also will detect Candida and Coccidioides. If cocci is suspected, write down "Look for cocci" on the Microbiology requisition. Additionally, Coccidioides immitis meningitis can be diagnosed by CSF culture, but culture is only about 50 % sensitive. Due to the low sensitivity and specificity, if cocci is suspected, we suggest also ordering serology on the CSF for coccidioides.

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2. Which common hematology tests require quick delivery to the clinical labs?

The following tests must be completed within two hours of specimen collection:

  • Cerebral spinal fluid (CSF) and body fluids for cell count and differential -- A time delay can result in cellular degeneration, thus adversely affecting results.
  • Urinalysis - This includes urine dipstick and microscopic examination.

The following test must be completed within four hours of specimen collection:

  • Coagulation tests - These include prothrombin time (PT) and partial thromboplastin time (PTT). Additional coagulation tests cannot be added to a specimen that has exceeded this time period from collection.

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