Browsing by Author "Rajasingham, Radha"

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    Cryptococcal Meningitis Diagnostics and Screening in the Era of Point-of-Care Laboratory Testing
    (Journal of clinical microbiology, 2019-01-02) Rajasingham, Radha; Katende, Andrew; Letang, Emilio; Boulware, David R.
    Over the past ten years, standard diagnostics for cryptococcal meningitis in HIV-infected persons have evolved from culture to India ink to detection of cryptococcal antigen (CrAg), with the recent development and distribution of a point-of-care lateral flow assay. This assay is highly sensitive and specific in cerebrospinal fluid (CSF), but is also sensitive in the blood to detect CrAg prior to meningitis symptoms. CrAg screening of HIV-infected persons in the blood prior to development of fulminant meningitis and preemptive treatment for CrAg-positive persons are recommended by the World Health Organization and many national HIV guidelines. Thus, CrAg testing is occurring more widely, especially in resource-limited laboratory settings. CrAg titer predicts meningitis and death and could be used in the future to customize therapy according to burden of infection.
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    Evaluation of the Diagnostic Performance of a Semiquantitative Cryptococcal Antigen Point-of-Care Assay among HIV-Infected Persons with Cryptococcal Meningitis
    (Journal of clinical microbiology, 2021) Tadeo, Kiiza Kandole; Nimwesiga, Audrey; Kwizera, Richard; Apeduno, Lucy; Martyn, Emily; Okirwoth, Michael; Nalintya, Elizabeth; Rajasingham, Radha; Williams, Darlisha A.; Rhein, Joshua; Meya, David B.; Kafufu, Bosco; Boulware, David R.; Skippera, Caleb P.
    A newly developed cryptococcal antigen (CrAg) semiquantitative (SQ) lateral flow assay (LFA) provides a semiquantitative result in a rapid one-step test instead of performing serial dilutions to determine CrAg titer. We prospectively compared the diagnostic performance of the CrAgSQ assay (IMMY) with the CrAg LFA (IMMY) on cerebrospinal fluid (CSF) samples collected from persons with HIV-associated meningitis. The CrAgSQ grades (1+ to 5+) were compared with CrAg LFA titers and quantitative CSF fungal cultures. Among 87 participants screened for HIV-associated meningitis, 60 had cryptococcal meningitis (59 CrAg positive [CrAg+] by LFA and 1 false negative due to prozone with CrAg LFA titer of 1:1,310,000 and culture positivity), and 27 had no cryptococcal meningitis by CrAg LFA or culture. The CrAgSQ on CSF had 100% (60/60) sensitivity and 100% specificity (27/27). CSF CrAg titers ranged from 1:5 to 1:42 million. CrAgSQ grades of 1+, 2+, 3+, 4+, and 5+ corresponded to median CrAg LFA titers of 1:<10, 1:60, 1:7,680, 1:81,920, and 1:1,474,000, respectively. CSF CrAgSQ grades 3+ or higher were always CSF culture positive. Mortality at 14 days for those with low CrAgSQ grade (1+ to 3+) was 5% (1/22) versus 21% (8/38) with high CrAgSQ grades (4+ to 5+) (P = 0.084). The CrAgSQ demonstrates excellent diagnostic performance, maintaining both the sensitivity and specificity of the CrAg LFA, and counters false-negative prozone effects. The CrAgSQ assay reading is more complex but does provide useful clinical information about disease burden and probability of culture positivity in a single rapid diagnostic test.
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    Minimum Inhibitory Concentration Distribution of Fluconazole Against Cryptococcus Species and the Fluconazole Exposure Prediction Model
    (US: Oxford University Press, 2019) Chesdachai, Supavit; Rajasingham, Radha; Meya, David B.; Bongomin, Felix; Abassi, Mahsa; Skipper, Caleb; Kwizera, Richard; Rhein, Joshua; Boulware, David R.
    Fluconazole is lifesaving for treatment and prevention of cryptococcosis; however, optimal dosing is unknown. Initial fluconazole doses of 100 mg to 2000 mg/day have been used. Prevalence of fluconazole nonsusceptible Cryptococcus is increasing over time, risking the efficacy of long-established standard dosing. Based on current minimum inhibitory concentration (MIC) distribution, we modeled fluconazole concentrations and area under the curve (AUC) relative to MIC to propose a rational fluconazole dosing strategy.We conducted a systematic review using the MEDLINE database for reports of fluconazole MIC distribution against clinical Cryptococcus isolates. Then, we utilized fluconazole concentrations from 92 Ugandans who received fluconazole 800mg/day coupled with fluconazole’s known pharmacokinetics to predict plasma fluconazole concentrations for doses ranging from 100 mg to 2000 mg via linear regression. The fluconazole AUC above MIC ratio were calculated using Monte Carlo simulation and using the MIC distribution elucidated during the systemic review.We summarized 21 studies with 11 049 clinical Cryptococcus isolates. Minimum inihibitory concentrations were normally distributed with a geometric mean of 3.4 µg/mL, median (MIC50) of 4 µg/mL, and 90th percentile (MIC90) of 16 µg/mL. The median MIC50 trended upwards from 4 µg/mL in 2000–2012 to 8 µg/mL in 2014–2018. Predicted subtherapeutic fluconazole concentrations (below MIC) would occur in 40% with 100 mg, 21% with 200 mg, and 9% with 400 mg. The AUC:MIC ratio >100 would occur in 53% for 400 mg, 74% for 800 mg, 83% for 1200 mg, and 88% for 1600 mg.Currently recommended fluconazole doses may be inadequate for cryptococcosis. Further clinical studies are needed for rational fluconazole dose selection.
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    Performance of Cryptococcal Antigen Lateral Flow Assay Using Saliva in Ugandans with CD4 ,<100
    (PloS one, 2014) Kwizera, Richard; Nguna, Joyce; Kiragga, Agnes; Nakavuma, Jesca; Rajasingham, Radha; Boulware, David R.; Meya, David B.
    Cryptococcal meningitis can best be diagnosed by cerebrospinal fluid India ink microscopy, cryptococcal antigen detection, or culture. These require invasive lumbar punctures. The utility of cryptococcal antigen detection in saliva is unknown. We evaluated the diagnostic performance of the point-of-care cryptococcal antigen lateral flow assay (CrAg LFA) in saliva.We screened HIV-infected, antiretroviral therapy naïve persons with symptomatic meningitis (n = 130) and asymptomatic persons with CD4+<100 cells/µL entering into HIV care (n = 399) in Kampala, Uganda. The diagnostic performance of testing saliva was compared to serum/plasma cryptococcal antigen as the reference standard.The saliva lateral flow assay performance was overall more sensitive in symptomatic patients (88%) than in asymptomatic patients (27%). The specificity of saliva lateral flow assay was excellent at 97.8% in the symptomatic patients and 100% in asymptomatic patients. The degree of accuracy of saliva in diagnosing cryptococcosis and the level of agreement between the two sample types was better in symptomatic patients (C-statistic 92.9, κ-0.82) than in asymptomatic patients (C-statistic 63.5, κ-0.41). Persons with false negative salvia CrAg tests had lower levels of peripheral blood CrAg titers (P<0.001).There was poor diagnostic performance in testing saliva for cryptococcal antigen, particularly among asymptomatic persons screened for preemptive treatment of cryptococcosis.