A location science model for the placement of POC CD4 testing devices as part of South Africa's public healthcare diagnostic service delivery model

Oosthuizen, Louzanne (2015-03)

Thesis (MEng)--Stellenbosch University, 2015.

Thesis

ENGLISH ABSTRACT: South Africa has a severe HIV (human immunodeficiency virus) burden and the management of the disease is a priority, especially in the public healthcare sector. One element of managing the disease, is determining when to initiate an HIV positive individual onto anti-retroviral therapy (ART), a treatment that the patient will remain on for the remainder of their lifetime. For the majority of HIV positive individuals in the country, this decision is governed by the results of a CD4 (cluster of differentiation 4) test that is performed at set time intervals from the time that the patient is diagnosed with HIV until the patient is initiated onto ART. A device for CD4 measurement at the point of care (POC), the Alere PIMA™, has recently become commercially available. This has prompted a need to evaluate whether CD4 testing at the POC (i.e. at the patient serving healthcare facility) should be incorporated into the South African public healthcare sector's HIV diagnostic service provision model. One challenge associated with the management of HIV in the country is the relatively large percentage of patients that are lost to follow-up at various points in the HIV treatment process. There is extensive evidence that testing CD4 levels at the POC (rather than in a laboratory, as is the current practice) reduces the percentage of patients that are lost to follow-up before being initiated onto ART. Therefore, though POC CD4 testing is more expensive than laboratory-based CD4 testing, the use of this technology in South Africa should be investigated for its potential to positively influence health outcomes. In this research, a multi-objective location science model is used to generate scenarios for the provision of CD4 testing capability. For each scenario, CD4 testing provision at 3 279 ART initiation facilities is considered. For each facility, either (i) a POC device is placed at the site; or (ii) the site's testing workload is referred to one of the 61 CD4 laboratories in the country. To develop this model, the characteristics of eight basic facility location models are compared to the attributes of the real-world problem in order to select the most suitable one for application. The selected model's objective, assumptions and inputs are adjusted in order to adequately model the realworld problem. The model is solved using the cross-entropy method for multi-objective optimisation and the results are verified using a commercial algorithm. Nine scenarios are selected from the acquired Pareto set for detailed presentation. In addition, details on the status quo as well as a scenario where POC testing is used as widely as possible are also presented. These scenarios are selected to provide decision-makers with information on the range of options that should be considered, from no or very limited use to widespread use of POC testing. Arguably the most valuable contribution of this research is to provide an indication of the optimal trade-off points between an improved healthcare outcome due to POC CD4 testing and increased healthcare spending on POC CD4 testing in the South African public healthcare context. This research also contributes to the location science literature and the metaheuristic literature.

AFRIKAANSE OPSOMMING: Suid-Afrika gaan gebuk onder `n swaar MIV- (menslike-immuniteitsgebreksvirus-) las en die bestuur van die siekte is `n prioriteit, veral in die openbare gesondheidsorgsektor. Een element in die bestuur van die siekte is om te bepaal wanneer `n MIV-positiewe individu met antiretrovirale- (ARV-)behandeling behoort te begin, waarop pasiënte dan vir die res van hul lewens bly. Vir die meeste MIV-positiewe individue in die land word hierdie besluit bepaal deur die uitslae van `n CD4- (cluster of differentiation 4-)toets wat met vasgestelde tussenposes uitgevoer word vandat die pasiënt met MIV gediagnoseer word totdat hy of sy met ARV-behandeling begin. `n Toestel vir CD4-meting by die punt van sorg (\POC"), die Alere PIMA™, is onlangs kommersieel beskikbaar gestel. Dit het `n behoefte laat ontstaan om te bepaal of CD4-toetsing by die POC (met ander woorde, by die gesondheidsorgfasiliteit waar die pasiënt bedien word) by die MIV-diagnostiese diensleweringsmodel van die Suid-Afrikaanse openbare gesondheidsorgsektor ingesluit behoort te word. Een uitdaging met betrekking tot MIV-bestuur in die land is die betreklik groot persentasie pasiënte wat verlore gaan vir nasorg in die verskillende stadiums van die MIV-behandelingsproses. Heelwat bewyse dui daarop dat die toetsing van CD4-vlakke by die POC (eerder as in `n laboratorium, soos wat tans die praktyk is) die persentasie pasiënte wat verlore gaan vir nasorg voordat hulle met ARV-behandeling kan begin, verminder. Daarom, hoewel CD4-toetsing by die POC duurder is as toetsing in `n laboratorium, behoort die gebruik van hierdie tegnologie in Suid-Afrika ondersoek te word. In hierdie studie is `n meerdoelige liggingswetenskapmodel gebruik om scenario's vir die voorsiening van CD4-toetsvermoë te skep. Vir elke scenario word CD4-toetsvermoë by 3 279 ARV-inisiasie fasiliteite oorweeg. Vir elke fasiliteit word toetsvermoë verskaf deur (i) die plasing van POC-toestelle by die fasiliteit, of (ii) verwysing vir laboratoriumgebaseerde toetsing by een van die 61 CD4-laboratoriums in die land. Die kenmerke van agt basiese fasiliteitsliggingsmodelle is met die kenmerke van die werklike probleem vergelyk om die mees geskikte model vir toepassing op die werklike probleem te bepaal. Die doelwitte, aannames en insette van die gekose model is daarna aangepas om die werklike probleem voldoende te modelleer. Die model is opgelos met behulp van die kruis-entropie-metode vir meerdoelige optimering, waarna die resultate deur middel van `n kommersiële algoritme bevestig is. Nege scenario's uit die verworwe Pareto-stel word uitvoerig aangebied. Daarbenewens beskryf die studieresultate die besonderhede van die status quo sowel as `n scenario waar POC-toetsing so wyd moontlik gebruik word. Hierdie scenario's word aangebied om besluitnemers van inligting te voorsien oor die verskeidenheid moontlikhede wat oorweeg kan word, wat wissel van geen of baie beperkte tot wydverspreide gebruik van POC-toetsing. Die mees beduidende bydrae van hierdie navorsing is stellig dat dit `n aanduiding bied van die optimale kompromie tussen `n verbeterde gesondheidsorguitkoms weens CD4-toetsing by die POC, en verhoogde gesondheidsorgbesteding aan CD4-toetsing by die POC, in die konteks van Suid-Afrikaanse openbare gesondheidsorg. Die navorsing dra ook by tot die ligingswetenskapliteratuur sowel as tot die metaheuristiekliteratuur.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/96972
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