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Point-of-care fingerstick CRAG provides low-cost, rapid meningitis diagnosis
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Fingerstick cryptococcal antigen lateral flow assay appeared to be a reliable bedside diagnostic test for meningitis, according to researchers in Uganda and the United States.
“[Cryptococcal antigen (CRAG)] testing of whole blood by capillary fingerstick had 100% concordance with serum or plasma CRAG results collected by venipuncture,” Darlisha Williams, of Makerere University in Kampala, Uganda, and colleagues wrote. “Fingerstick CRAG had 100% negative predictive value for excluding cryptococcal meningitis.”
From August 2013 to August 2014, the investigators prospectively examined 207 patients with HIV and suspected meningitis who were admitted to the Mulago National Referral Hospital in Uganda. Fingerstick CRAG lateral flow assay (LFA) tests on whole blood, plasma/serum and cerebrospinal fluid (CSF) were performed, and compared with a composite reference standard.
The researchers found 72% of the patients were fingerstick CRAG-positive for cryptococcosis, and there was 100% agreement between fingerstick whole blood and serum/plasma screening, according to the investigators. Ninety-three percent of the fingerstick CRAG-positive patients had a CSF CRAG test that was positive for cryptococcal meningitis. Eleven patients had isolated cryptococcal antigenemia with a negative CSF CRAG and culture, including eight with CSF abnormalities. No patients with cryptococcal meningitis had negative fingersticks.
The use of reliable fingerstick CRAG testing bypasses a “clinical management paradox,” the researchers wrote. A cryptococcal meningitis diagnosis can only be confirmed with a lumbar puncture (LP); however, this delay means the opportunity to remove sufficient CSF to normalize intracranial pressure is often missed.
“By CRAG screening prior to the LP, one can prioritize on whom to measure opening pressure or empirically remove 20 mL to 25 mL CSF, which was the median amount removed in this cohort,” the researchers wrote.
“Using the fingerstick CRAG LFA as a rapid initial step toward establishing a diagnosis can enable better treatment. Fingerstick CRAG testing represents an important and simple tool for meningitis diagnosis worldwide,” they concluded. – by Colleen Owens
Disclosure: The researchers report no relevant financial disclosures.
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