Fig. 3

Difference in unit cost of more centralized versus more decentralized Xpert testing for tuberculosis (TB). Shown on the y-axis is the range of difference in mean per-test cost of Xpert test (inclusive of equipment, consumables, sample transport, human resources, and overheads) performed in the centralized scenario (district-level testing with sample transport network, assuming a range between 5 (“high cost sharing”) and 100% (“exclusive TB sample transport”) of this network—represented by the size of each bar—is used for sputum specimens/TB testing) and in the decentralized scenario (testing at the microscopy center level). Values above the horizontal line ($0, gray dotted line) denote that decentralized testing is more expensive than centralized testing, whereas values below that line denote that centralized testing is more costly. The dumbbell dot plot on the left represents a setting where a mean of 0.3 tests are performed per day at the peripheral level (i.e., smaller, low-volume clinics), whereas those on the right represent a mean volume of 3 tests per day. The seven boxes in each series represent, from left to right, increasing mean test volume of 10 to 70 or more tests per day at the centralized testing facility. Such variation might be seen, for example, if an increasing number of peripheral clinics referred specimens to the same district center, or if the district center performed testing for other purposes (e.g., inpatients, drug susceptibility testing). In general, increasing testing volume makes maximal use of equipment and sample transport network costs, such that higher test volumes in the periphery favor decentralized testing, whereas higher test volumes at the district level favor centralized testing. Full assessment of all scenarios is available in Additional file 1: Section 1.5 and Figure S3