Magazine article Journal of Continuing Education Topics & Issues

Three Rapid Screening Tests for Cryptococcus Neoformans in the Laboratory

Magazine article Journal of Continuing Education Topics & Issues

Three Rapid Screening Tests for Cryptococcus Neoformans in the Laboratory

Article excerpt

Three Rapid Screening Tests for Cryptococcus Neoformans in the Laboratory

It is imperative that clinicians and medical laboratorians, primarily medical technologists, are reintroduced to three rapid screening tests used in the detection of Cryptococcus neoformans. The severity of individuals co-infected with Cryptococcus neoformans and HIV often result in a fatal outcome; therefore, these three presumptive laboratory tests, cell count, India ink, and gram stain, are of clinical importance. The purpose of this case report is to recount the clinical experience of a patient; identify causative agent of his medical condition, highlight treatment management, outcome, and recognize the diagnostic laboratory tests used in the assessment process. A brief literature review is provided that includes the lack of research evidence identifying Cryptococcus neoformans within the Caribbean region. The discussion will focus on clinical implications of the report, why it is important to disseminate these findings to clinicians and medical laboratorians, and options of advanced technological methods to identify the opportunistic pathogen.

A patient suspiciously infected with Cryptococcus neoformans will need rapid laboratory testing and aggressive medical intervention for the preservation of life. Awareness of the concurrent use of the three tests is expected to increase their application in medical laboratories. According to World Health Organization (WHO), "rapid tests are better for emergency testing.... designed for use where a preliminary screening test result is required and are especially useful in resource-limited countries.... Quick and easy to perform--10 minutes to 2 hours" (2017, p. 1). Cerebrospinal fluid (CSF) is the specimen of choice for laboratory investigation of Cryptococcus neoformans (C. neoformans) found in the central nervous system (CNS).

Case Description

A 29-years-old male, who was an agriculture farmer and pigeon owner, presented himself at the emergency room (ER) at first visit, and with no prior medical history. He complained of a headache, sensitivity to light, and nausea. The attending physician ordered routine laboratory tests that were performed by experienced medical technologists. The tests included complete blood count, chemistry seven-panel, and urinalysis; at the time no CSF was ordered. The results of the laboratory tests were within normal ranges. Treated for a migraine, the patient was discharged and advised to return to the ER should the symptoms worsen. Four days later, he returned to the ER with complaints of a severe headache, confusion, stiff-neck, increased sensitivity to light, fever, vomiting, and episodes of seizures. The patient was admitted for diagnostic assessment. Based on the physician's clinical experience, and the patient's signs and symptoms, laboratory tests were ordered that required peripheral blood samples and approximately three--five milliliters of CSF in vials, obtained by performing a lumbar puncture.

Relevant Laboratory Investigations

Upon receipt in the laboratory, the physical appearance of the slightly cloudy and colorless CSF sample was the first indication of an infection. According to Rao (2006), CSF samples collected are often separated into three parts for (a) protein and glucose analysis, (b) cell count, and (c) microbiological examination, after centrifugation. The sediment from the centrifuged sample was used for India ink, gram stain, and fungal culture: A portion of the sediment was inoculated onto Sabouraud's dextrose agar, incubated at 25[degrees]C for 48 hours, and observed for microbial growth.

CSF cell count test. A traditional manual method for counting undiluted cells in CSF, based on the expected low cell number encountered.

Using the glass Neubauer counting chamber:

* Two hundred microliters of CSF was added to 150 [micro]l of Turk's solution into a test tube.

* A drop of mixed suspension was placed on both sides of the charged glass chamber. …

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