Establishing a cost-per-result of laboratory-based, reflex Cryptococcal antigenaemia screening (CrAg) in HIV+ patients with CD4 counts less than 100 cells/μl using a Lateral Flow Assay (LFA) at a typical busy CD4 laboratory in South Africa.
BACKGROUND
Cryptococcal meningitis is a major cause of mortality and morbidity in countries with high HIV prevalence, primarily affecting patients whose CD4 are < = 100 cells/μl. Routine Cryptococcal Antigen (CrAg) screening is thus recommended in the South African HIV treatment guidelines for all patients with CD4 counts < = 100 cells/μl, followed by pre-emptive anti-fungal therapy where CrAg results are positive. A laboratory-based reflexed CrAg screening approach, using a Lateral Flow Assay (LFA) on remnant EDTA CD4 blood samples, was piloted at three CD4 laboratories.


OBJECTIVE
This study aimed to assess the cost-per-result of laboratory-based reflexed CrAg screening at one pilot CD4 referral laboratory.


METHODS
CD4 test volumes from 2014 were extracted to estimate percentage of CD4 < = 100 cells/μl. Daily average volumes were derived, assuming 12 months per/year and 21.73 working days per/month. Costing analyses were undertaken using Microsoft Excel and Stata with a provider prospective. The cost-per-result was estimated using a bottom-up method, inclusive of test kits and consumables (reagents), laboratory equipment and technical effort costs. The ZAR/$ exchange of 14.696/$1 was used, where applicable. One-way sensitivity analyses on the cost-per-result were conducted for possible error rates (3%- 8%, reductions or increases in reagent costs as well as test volumes (ranging from -60% to +60%).


RESULTS
The pilot CD4 laboratory performed 267000 CD4 tests in 2014; ~ 9.3% (27500) reported CD4< = 100 cells/μl, equivalent to 106 CrAg tests performed daily. A batch of 30-tests could be performed in 1.6 hours, including preparation and analysis time. A cost-per-result of $4.28 was reported, with reagents contributing $3.11 (72.8%), while technical effort and laboratory equipment overheads contributed $1.17 (27.2%) and $0.03 (<1%) respectively. One-way sensitivity analyses including increasing or decreasing test volumes by 60% revealed a cost-per-result range of $3.84 to $6.03.


CONCLUSIONS
A cost-per-result of $4.28 was established in a typical CD4 service laboratory to enable local budgetary cost projections and programmatic cost-effectiveness modelling. Varying reagent costs linked to currency exchange and varying test volumes in different levels of service can lead to varying cost-per-test and technical effort to manage workload, with an inverse relationship of higher costs expected at lower volumes of tests.
National Health Laboratory Service (NHLS), National Priority Programmes, Johannesburg, South Africa.|Department of Molecular Medicine and Haematology, Faculty of Health Sciences, University of Witwatersrand, Johannesburg, South Africa.
Naseem
N
Cassim
Right to Care, Johannesburg, South Africa.
Kathryn
K
Schnippel
National Health Laboratory Service (NHLS), National Priority Programmes, Johannesburg, South Africa.|Department of Molecular Medicine and Haematology, Faculty of Health Sciences, University of Witwatersrand, Johannesburg, South Africa.
Lindi Marie
LM
Coetzee
National Health Laboratory Service (NHLS), National Priority Programmes, Johannesburg, South Africa.|Department of Molecular Medicine and Haematology, Faculty of Health Sciences, University of Witwatersrand, Johannesburg, South Africa.
Deborah Kim
http://orcid.org/0000-0001-7106-769X
DK
Glencross
D017088:AIDS-Related Opportunistic Infections; D000935:Antifungal Agents / Q000627:therapeutic use; D000946:Antigens, Fungal / Q000276:immunology; D018791:CD4 Lymphocyte Count; D003362:Cost-Benefit Analysis; D003453:Cryptococcosis / Q000175:diagnosis* / Q000188:drug therapy / Q000276:immunology*; D003454:Cryptococcus / Q000276:immunology*; D005260:Female; D015658:HIV Infections / Q000150:complications* / Q000276:immunology*; D006801:Humans; D007118:Immunoassay / Q000191:economics*; D008297:Male; D008403:Mass Screening / Q000191:economics; D012680:Sensitivity and Specificity
D000935:Antifungal Agents; D000946:Antigens, Fungal