Page 260 - Read Online

Guo et al. Diagnosis and treatment of cryptococcal meningitis

interstitial fluid. [15,16] The appearance of CSF is clear distribution. Therefore, the detection method requires
and transparent generally, and it can be slightly turbid high skill levels from observers. Alcian blue staining
if there is a large amount of Cryptococcus. Leukocyte is a special dye for the C. neoformans and could
[25]
count in CSF is increased (about 100-500 × 10 /L) in dye the capsule to be deep blue, and the cell light
6
the majority of people, or normal in the minority. In blue, without the peripheral inflammatory cells being
addition, the protein level rises (no more than 2 g/L dyed. Therefore, the sensitivity of alcain blue staining
usually), and the glucose and chloride decreases in is high and the fungi can be easily observed. The
[26]
CSF as the result of infection. The degree of decrease combination of the above methods can improve the
in glucose levels is significantly lower than that of other detection rate. Culture is considered the gold standard
central nervous system infection. [17] for diagnosis of cryptococcal meningitis. But it
[27]
is limited by culture conditions, culture time and the
The characteristics of cerebrospinal fluid cytology: amount of cerebrospinal fluid and fungi, thus making
the total number of cells increases to different the early diagnosis hampered. But it has important
degrees, presenting mixed cell reaction or lymphocyte value for further drug sensitivity test and species
dominated mixed cell reaction. Monocyte constitutes classification.
the main ingredients in the most of the cerebrospinal
fluid cytology of CM patients, the total number of cells The most reliable diagnostic method for cryptococcosis
decreases and the proportion of small lymphocytes is to detect capsular polysaccharide antigen which
[20]
also increases with the improvement of the disease. can be find in serum, CSF, and urine specimens. Serum
Therefore, cerebrospinal fluid cytology has also certain CrAg is taken as an early biologic marker which is far
significance to the monitoring of the efficacy. more sensitive and rapid than direct detection of the
pathogen, it highly predicts of the development of CM
However, cerebrospinal fluid examination is normal in within one year. Retrospective data suggests that
[28]
10-17% other patients, especially in the patients with CrAg screening in patients with late-stage human HIV
HIV. [18,19]
ART may reduce cryptococcal disease and deaths.
[29]
Other laboratory examination However, presence of CrAg in CSF is more valuable
The common laboratory examination for diagnosing of for diagnosis of CM and serum CrAg assay can help to
CM mainly includes morphological examination, fungal assist the diagnosis.
culture, and antigen detection.
Main methods are consist of latex agglutination (LA)
Cryptococcus neoformans (C. neoformans) is a single- assays, enzyme immunoassays (EIAs), or the novel
[20]
celled organism with a polysaccharide capsule. It lateral flow assay (LFA). LA or EIAs has been used for
[30]
exists in the blood, CSF, and tissues. Morphological detecting CrAg for several years. The sensitivity and
[20]
diagnosis depends on dyeing technology. India ink specificity of the LA test for CSF is high. The sensitivity
staining is considered to be one of the gold standards ranges from 93% to 100%, while the specificity ranges
for diagnosis. It is a traditional method of identification from 93% to 98%, which is significantly better than India
of C. neoformans, especially in areas with limited ink staining and CSF cytology in the early diagnosis of
resources because of its simple and rapid operation. CM. And the severity of the disease in patients with
Characteristic “starry night” phenomenon would be cryptococcal meningitis is correlated with the antigen
[20]
observed by India ink staining: capsule is not shaded titer of capsular polysaccharide, therefore, LA test also
but surrounded dyed blue. Yet the sensitivity of india has the value of evaluating the severity of illness and the
[31]
ink staining is only < 86%. [21,22] In addition, due to low prognosis. Although this method has high sensitivity,
fungal loads, India ink is insensitive for patients who but may appear false positive results in patients with
presenting early after symptoms appear or being on immunological diseases, such as rheumatoid. [32,33]
initiating antiretroviral therapy (ART). The detection Tedious manual operation and subjective intervention
[23]
rate of C. neoformans in the CSF is only 66% at first is the main weakness, in addition, this method
time, about 17.8% at second time, and others remain needs equipment and refrigeration which restricts its
[20]
3 to 20 times smear test under microscope to find application in resource limited area. The sensitivity
positive. May-Grunwald-Giemsa (MGG) staining has and specificity of EIAs test for capsular polysaccharide
[24]
a relatively high positive detection rate, a small amount antigen is high which is 100% and 98% respectively
of C. neoformans can be detected after centrifugal for CSF samples. [34,35] However, EIAs test cannot be
precipitation, applying to patients with low amount of widely used because of the expensive detection kits.
fungi. But the morphological characteristics of the fungi
are not clear, it is easy to be confused with small lymph The lateral flow assay (LFA) is developed in 2009, it
cells in CSF when the C. neoformans scattered in the could detect cryptococcal polysaccharide capsule
Neuroimmunology and Neuroinflammation ¦ Volume 3 ¦ November 18, 2016 251