67 The serum antibody test is not useful because healthy persons in endemic areas frequently have positive test results, and many patients with cryptococcal meningitis have negative test results. In such cases, the diagnosis can be established by indirect immunofluorescence staining or reformation of the capsule by inoculation into mice. 66 The possibility of capsule-deficient cryptococcal meningitis should be considered in the rare event that the diagnosis is strongly suspected but the staining and antigen detection tests are negative. False-positive results occur, but other tests, such as EIA, are more sensitive and specific. Both blood and CSF should be tested for cryptococcal antigen. When a CSF specimen is tested, pronase treatment is not needed (but such treatment does improve results when serum is tested). The commercially available latex agglutination test detects antigen in more than 90% of patients with cryptococcal meningitis. Large volumes of CSF (5 to 10 mL) should be removed for culture on at least three occasions to increase the yield of isolation.ĭetection of cryptococcal antigen in CSF is the most clinically useful test. The test is positive in 50% of patients, but false-positive results can occur culture of a CSF sample is required to confirm the diagnosis. The India ink stain or the fluorescent stain (the commercially available Calco-Fluor white stain) is important in screening CSF samples of patients with suspected cryptococcal meningitis. Ram Yogev, in Principles and Practice of Pediatric Infectious Disease (Third Edition), 2008 Cryptococcus Species Despite the advantages for clinical applications, India ink has some limitations, including a tendency to diffuse and moderate EPR sensitivity. The suitability of the clinical EPR system for pO 2 measurements in superficial tumors (< 10 mm depth) using India ink has been demonstrated for locations ranging from the feet, to the anterior and posterior surfaces of the torso, and scalp ( Khan, Williams, Hou, Li, & Swartz, 2007 Khan et al., 2006 Swartz, Hou, et al., 2014 Swartz, Williams, et al., 2014 Williams et al., 2010).
In preclinical studies, we have extensively used oxygen-sensitive India ink as a probe to measure the effects of split-dose radiation on the oxygenation of RIF-1 and MTG-B tumors in mice ( Jiang et al., 1996 Nakashima et al., 1995 O'Hara et al., 1998).
Given the fact that some of the India inks have already been used as a tissue marker in patients for several decades, they can also be used for oximetry in patients provided they have oxygen-sensitive carbon particles. The preparation and biocompatibility testing of oxygen-sensitive inks for EPR oximetry have been described previously ( Charlier, Beghein, & Gallez, 2004 Gallez et al., 1998 Gallez & Mader, 2000 Jordan et al., 1998). Fortuitously, carbon black particles in some of the India ink formulations contain stable radical species at sufficient concentrations with EPR signals that are sensitive to the presence of oxygen ( Goda et al., 1995 Jiang et al., 1996 Jordan, Baudelet, & Gallez, 1998 Khan et al., 2005 Nakashima, Goda, Jiang, Shima, & Swartz, 1995 O'Hara, Goda, Demidenko, & Swartz, 1998 Swartz, Hou, et al., 2014 Swartz, Liu, Goda, & Walczak, 1994 Swartz, Williams, et al., 2014 Williams et al., 2010) ( Fig. India ink also has a long history of clinical use as an anatomic marker for surgery and radiotherapy. India ink is a suspension of carbon black particles in a medium (such as ethylene glycol) and is commonly used in pens for writing, drawing, or epidermal tattooing.
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