Tuberculosis case detection in Nigeria, the unfinished agenda.

Objective: Underdetection of TB is a major problem in sub-Saharan Africa. WHO recommends countries should have at least 1 laboratory per 100,000 population. However, this recommendation is not evidence based.

Methods: We analysed surveillance data of the Nigerian National TB Control Programme (2008-2012) to describe TB case detection rates, their geographical distribution and their association with the density of diagnostic laboratories and HIV prevalence.

Results: The median CDR was 17.7 (range 4.7-75.8%) in 2008, increasing to 28.6% (range 10.6-72.4%) in 2012 (P < 0.01). The CDR2012 was associated with the 2008 baseline; however, states with CDR2008 < 30% had larger increases than states with CDR2008 > 30. There were 990 laboratories in 2008 and 1453 in 2012 (46.7% increase, range by state -3% to +118). The state CDR2012 could be predicted by the laboratory density (P < 0.001), but was not associated with HIV prevalence or the proportion of smear-positive cases. CDR2012 and laboratory density were correlated among states having < and > than 1 laboratory per 100,000 population.

Conclusion: There are large variations in laboratory density and CDR across the Nigerian states. The CDR is associated with the laboratory density. A much larger number of diagnostic centres are needed. It is likely that a laboratory density above the recommended WHO guideline would result in even higher case detection, and this ratio should be considered a minimum threshold.