Genexpert system

During the study period, C difficile testing was performed only on unformed stool samples on specific request by physicians. Before November 2011, the presence of C difficile was assessed by enzyme immunoassay (EIA; ImmunoCard Toxins A&B, Meridian Biosciences) of fresh stool samples coupled with culture (algorithm, Alg1). For culture, stool samples were plated on CLO medium (Biomérieux) and incubated in anaerobic conditions at 37°C for 48 hours. If the assay yielded negative toxin results and the culture was positive for C difficile, isolate toxicity was assessed in vitro (toxigenic culture). Between November 2011 and January 2013, an algorithm protocol was used involving glutamate dehydrogenase (GDH) (ImmunoCard C difficile GDH assay; Meridian Biosciences) antigen screening test, and if it was positive, stools were subsequently tested for C difficile toxins A and B by EIA and culture as previously described (Alg2). Beginning in February 2013, the laboratory replaced the last algorithm with a combined immunochromatographic test of GDH and toxins (C. DIFF QUIK CHEK COMPLETE; Alere) coupled with polymerase chain reaction (PCR) (GeneXpert Systems, Cepheid). If the screening test was positive and the toxins were negative, PCR was then performed as a confirmatory test (Alg3).

As a comparator, the cost per result was determined for traditional laboratory-based Xpert MTB/RIF testing. Initial laboratory setup included the installation of the four GeneXpert systems (Cepheid, Sunnyvale, California, United States) (capacity of 64 samples per day), an air conditioner, a level two biosafety hood and a vortex mixer. Operational costs included costs to procure reagents, consumables, specimen collection materials, quality control materials (internal and external), printer cartridges and paper. The assumptions for these operational costs were similar to those for mobile testing.
The staff complement required to perform mobile testing included a medical technologist and a laboratory manager, who provided minimal supervision. The technologists performed other testing in addition to Xpert MTB/RIF. The costs of the business management unit (coordinator costs) in the North West province were determined and included the following personnel: business manager, secretary, quality assurance coordinator, human resources officers, training staff, and other support staff. To determine the coordinator costs per result, the AEC was divided by the annual test volume for the province. For the courier costs, the annual expenditure for the laboratory was used.