1. CrAg titers- To know or not to know
Fungal Diagnostics for Advanced HIV Disease Workshop
Kampala April 2018

2. The Literature
Cryptococcal colony-forming unit counts & CSF cryptococcal antigen (CrAg) titers serve as alternative measures of organism load in cryptococcal disease
Strong correlation between CSF cryptococcal colony-forming unit (CFU) counts and CSF cryptococcal antigen titers observed at baseline in Cryptococcal meningitis
Decrease of >5 logs in CFUs and 1.5 dilutions during induction therapy
No correlation between rate of decline in CFUs and titers in individual patients
Brouwer AE, et al J Inf Dis2005

3. The Literature
Majority of patients (87%) had serum CrAg (sCrAg) titers decrease over time, in a UCSF study
No significant correlation between sCRAG titer results of patients who had a clinical response to treatment and sCRAG titers in patients who experienced persistent disease, probable relapse, or definitive relapse of cryptococcal disease
Monitoring of sCRAG titer is not useful in the management of patients with AIDS-related cryptococcal disease on treatment
Aberg JA, et al HIV Clin Trials, 2000

4. Asymptomatic Cryptococcal Disease
Risk of developing Cryptococcal meningitis in asymptomatic CrAg+ patients associated with titer >1:160 (Letang E, OFID 2015)
Survival among CrAg+ patients was among patients with titer ≦ 1:128 in an Ethiopian study (Smitson C, et al PLOS One 2013)
Serum Titers > 1:160 strongly correlated with proven CM and Biosynex CryptoPS T2-band positivity (Temfack E, et al Frontiers in Micro 2018)

5. Asymptomatic Cryptococcal Disease
Data from ORCAS study, Uganda (Unpublished)

6. Outcomes and Titer change between CrAg Screening & Fluconazole start
ORCAS Study Unpublished

7. Asymptomatic Cryptococcal Disease
CRAG Screened
(CD4<100 cells/µL)
Asymptomatic plasma CRAG+ enrolled
Symptomatic
Accepted lumbar puncture
Declined lumbar puncture
p value
Number
1440 53 19 7
Women --
26 (49%)
13 (68%)
3 (43%)
0.65
Age, years 32
(29 to 39)
(29 to 41) 27
(24 to 31)
0.34
CD4 cells/µL 40
(17 to 70) 20
(5 to 45) 29
(12 to 45) 9
(6 to 17)
0.50
On ART
193 (13%)
9 (17%)
1 (5%)
0 (0%)
0.15
CRAG titer
1:40
(1:20 to 1:160)
1:160
(1:40 to 1:1280)
(1:20 to 1:60)
0.078
CRAG titer* >1:160
15 (32%)
10 (53%)
1 (14%)
0.29
Nalintya E, et al, JAIDS March 2018

8. Grey area in the middle where it is unclear whether they are closer to the left or Right
How does the serum titer match up with the CSF titer?

9. Tests for quantification of Titers
IMMY CrAg SQ LFA allows semi-quantitative detection of cryptococcal antigen in serum, plasma, whole blood and CSF.  The CrAg SQ LFA has two test lines (T1 and T2).  The T1 test line is the same as the CrAg LFA with a limit of detection of approximately 1 ng/ml. 
The T2 test line is an inhibition line with a limit of detection of approximately 160 ng/ml (1:160 titer). 
T2 has antigen on membrane instead of capture antibody.  T2 is positive when the line disappears. 
This unique design allows for four test results Biosynex CryptoPS- Semi quantitative with 2 bands- T1-band qualitative band and a T2 band with a titer cut off of 1: 100
EIA
Latex agglutination

10. Clinical Utility Ideally a modified LFA with semi-quantitative bands
What cut off should be used?
What to do with higher titer patients remains unknown
Would higher titer patients, ?>1: 160 be considered to have possible early cryptococccal meningitis and do they require a different standard of care?

11. References
Temfack E, Kouanfack C, Mossiang L, Loyse A, Fonkoua MC, Molloy SF, Koulla-Shiro S, Delaporte E, Dromer F, Harrison T and Olivier Lortholary. Cryptococcal Antigen Screeningin Asymptomatic HIV- Infected Antiretroviral Naïve Patients in Cameroon and Evaluation of the New Semi-Quantitative Biosynex CryptoPS Test. Front. Microbiol. 9:409.doi: /fmicb
Emilio Letang, Müller MC, Ntamatungiro AJ, Kimera N, Faini D, Furrer H, Battegay M, Tanner M, Hatz C, Boulware DR, and Glass TR. Cryptococcal Antigenemia in Immunocompromised Human Immunodeficiency Virus Patients in Rural Tanzania: A Preventable Cause of Early Mortality. OFID DOI: /ofid/ofv046
Nalintya E, Meya DB, Lofgren S, Hullsiek KH, Boulware DR, Rajasingham R. A Prospective Evaluation of a multisite Cryptococcal Screening and Treatment program in HIV clinics in Uganda JAIDS 2018 (In Press).
Smitson CC, Tenna A , Tsegaye M , Alemu AS , Fekade D , Aseffa A , Blumberg HM, Kempker RR. No Association of Cryptococcal Antigenemia with Poor Outcomes among Antiretroviral Therapy- Experienced HIV-Infected Patients in Addis Ababa, Ethiopia. PLoS ONE 9(1): e doi: /journal.pone