Research Article: Programmatic implications of implementing the relational algebraic capacitated location (RACL) algorithm outcomes on the allocation of laboratory sites, test volumes, platform distribution and space requirements

Date Published: February 28, 2017

Publisher: AOSIS

Author(s): Naseem Cassim, Honora Smith, Lindi M. Coetzee, Deborah K. Glencross.


CD4 testing in South Africa is based on an integrated tiered service delivery model that matches testing demand with capacity. The National Health Laboratory Service has predominantly implemented laboratory-based CD4 testing. Coverage gaps, over-/under-capacitation and optimal placement of point-of-care (POC) testing sites need investigation.

We assessed the impact of relational algebraic capacitated location (RACL) algorithm outcomes on the allocation of laboratory and POC testing sites.

The RACL algorithm was developed to allocate laboratories and POC sites to ensure coverage using a set coverage approach for a defined travel time (T). The algorithm was repeated for three scenarios (A: T = 4; B: T = 3; C: T = 2 hours). Drive times for a representative sample of health facility clusters were used to approximate T. Outcomes included allocation of testing sites, Euclidian distances and test volumes. Additional analysis included platform distribution and space requirement assessment. Scenarios were reported as fusion table maps.

Scenario A would offer a fully-centralised approach with 15 CD4 laboratories without any POC testing. A significant increase in volumes would result in a four-fold increase at busier laboratories. CD4 laboratories would increase to 41 in scenario B and 61 in scenario C. POC testing would be offered at two sites in scenario B and 20 sites in scenario C.

The RACL algorithm provides an objective methodology to address coverage gaps through the allocation of CD4 laboratories and POC sites for a given T. The algorithm outcomes need to be assessed in the context of local conditions.

Partial Text

The National Health Laboratory Service (NHLS) of South Africa provides national coordination for the laboratory service, staff training, quality control and quality assurance, as well as managing the overall quality management system. Within the national network of 266 laboratories, CD4 testing is currently offered at 59 laboratories to facilitate the staging and monitoring HIV-infected patients. These laboratories operate all levels of pathology service, including routine diagnostic chemical pathology, haematology and microbiology services. CD4 testing is offered using an integrated tiered service delivery model (ITSDM) that matches daily testing demand with appropriate testing capacity. This is required to manage laboratory workload, turn-around-time (TAT), instrument capacity utilisation and cost.1,2 CD4 testing is standardised using Beckman Coulter (Beckman Coulter, Miami, Florida, United States) equipment and the PanLeucoGating platform.3,4 In 2014, the NHLS performed 3.9 million CD4 tests.

The RACL algorithm outcomes reported an inverse relationship between T and the numbers of CD4 laboratories/POC sites required to provide coverage. This indicates that the number of CD4 laboratories required to ensure coverage would increase with a decreasing T. As T is increased, it would be possible to ensure coverage with fewer laboratories. The key would be to establish a T that could deliver a clinically-acceptable TAT in line with the standard of care. The current South African guidelines require a CD4 count within seven days to fast-track patients ≤ 200 cells/µL.11




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