TB laboratory network in Tanzania is arranged into four tiers contingent on the type of services provided:
Figure 21: TB Laboratory Network Structure
The TB diagnostic services are offered through Acid Fast Bacilli (AFB) smear microscopy (1,859 sites), Molecular WHO-recommended rapid diagnostics (mWRDs) testing (37 TrueNat and 306 GeneXpert sites), 5 Line Probe Assay (LPA) sites, 6 sites performing solid TB culture using Lowenstein Jensen (LJ) medium and 4 sites with the capacity to undertake liquid culture using Mycobacteria Growth Indicator Tube (MGIT) by BACTEC 960®.
The network has one Standalone TB laboratory that serves as a National Reference Laboratory commonly known as The Central Tuberculosis Reference Laboratory (CTRL). In addition, the CTRL can perform DST for first-line drugs (FLD) and second-line drugs (SLD) in both solid (LJ) and liquid (MGIT) media methods.
In Tanzania, the recommended initial tests for TB diagnosis are smear microscopy, TrueNat, and GeneXpert: Xpert/MTB Rif. To ensure new and previously treated TB cases are tested using mWRDs at the time of diagnosis, sites with only smear microscopy should send specimens to GeneXpert or TrueNat sites using the available integrated specimen referral system.
In 2023, a total of 6,384 specimens were received at the CTRL and ZCL. Out of all the specimens, 3,470 (54.4%) were at the CTRL and 2,914 (45.6%) at ZCL as shown in Table 1 and Table 2.
Table 1: Specimen Type received at the CTRL by 2023
Specimen Rejection
A total of 142 specimens were rejected in the year due to different reasons. Table 1 shows several specimens rejected and rejection rate at each Zonal TB culture laboratory. The Public Health Laboratory (PHL) and Dodoma Regional Referral Hospital TB culture laboratories have a high rejection rate of 6.5% and 6.8% respectively compared to other laboratories.
Figure 23 displays reasons for specimen rejection at CTRL in 2023: 38% insufficient volume specimen, 30% specimen leakage, 8% specimen collected in an improper container, 6% request form received without specimens, and 6% rejected because of prolonged transit time.
Figure 23: Reason for Specimens Rejection
Routine Surveillance System (Dr-TB)
Routine Surveillance System (RSS) refers to the systematic process of collecting, analysing, and interpreting the epidemiological profile resistance. The RSS is performed by collecting specimens for TB culture and DST from health facilities. The specimens are submitted to ZCL. Each facility is required to send 25% of new bacteriologically confirmed TB cases and 100% of previously treated cases for culture and DST.
In 2023, 37,142 were new bacteriologically confirmed TB cases, of which only 2,485 (6.7%) were received, similarly, 2,710 previously treated cases were notified and only 1,291 (47.63%) were received for culture and DST testing. It is evident that the number submitted for RSS is too low (Table 3).
Table 2: Sample Received Among Notified Cases
Key: Previously treated TB cases – Retreatment
Culture Indicators
All TB zonal culture laboratories performed the solid LJ method except the CTRL which performed both solid and liquid culture methods. The specimens tested by liquid culture at CTRL were 233 with final results of 64 positive, 167 negative, and 2 contaminated samples. A total of 5756 specimens were tested by solid culture. Majorities of LJ culture tests were performed at the CTRL with the highest positivity rate of 23% while PHL had the lowest positivity rate of 4%
Figure 24: Specimens with culture results in 2023
There are important culture indicators monitored periodically. Despite the culture indicators deviating from the recommended values at the CTRL, mitigation measures carried out have shown improvement toward the targets compared to the previous year as illustrated in Table 4
Table 3: CTRL Solid Culture (LJ) indicators
Among the 93,250 TB cases notified in 2023, 31,232 were bacteriologically confirmed TB cases through Xpert/MTB Rif equivalent to 33% of all cases. Whereas, 331 Rifampicin resistant TB cases were notified. The CTRL continues to monitor all GeneXpert operations in all sites across the country. A total of 218,553 GeneXpert MTB tests were uploaded into the GeneXpert National server for the year, these include routine tests, EQA, Internal Quality Control (IQC), verification tests, research purposed tests. The results have indicated a substantial number of tests are still not uploaded to the National server. The other important indicators such as error or invalid rates were within recommendation but the “No result” rate was beyond the recommended rate of 2.0% due to lack of power backups during interruptions.
Table 4: GeneXpert TB Tests uploaded in Aspect in 2023
Through the Tuberculosis Implementation Framework Agreement (TIFA) support for the TB diagnostic network, 3 XDR machines were installed in Zonal TB culture laboratories at KIDH, DRRH and MZRH-NIMR making a total of 4 GeneXpert MTB XDR machines across the network including the one at the CTRL installed in 2021 by Cepheid. All the GeneXpert MTB/ XDR Machines have been integrated into the DHIS2-ETL and they upload the test results to the system using a specific TB case district number.
Table 5: GeneXpert: Xpert/MTB XDR Results in 2023
The CTRL carried on with TB molecular diagnostic technologies implementation activities countrywide through the implementation of various activities such as training, supportive supervisions, mentorships, developing and reviewing of training materials, Standard operating procedures (SOPs), and supervision tools. Additionally, maintenance and calibration of machines, as well as troubleshooting of machines and the GxAlert system when necessary. The CTRL continues scaling up the WHO-recommended technologies and monitors data through the web-based GxAlert/Aspect system as well as manual compilation through Quickstat.
By the end of 2023, there were 342 GeneXpert devices installed in 306 sites countrywide, an increase of 6 machines compared to 2022, 4 of which are Xpert/MTB XDR, a new technology capable of detecting resistance to Fluoroquinolones. Out of the 342; 328 (96%) machines are used for routine Testing and 14 (4%) machines are used for research purposes.
Despite the successes of GeneXpert technology, it still faces some operational limitations. The need for electricity power backup and specific temperature requirements in laboratories are difficult to guarantee in many remote and hard-to-reach health facilities. These challenges limit the accessibility of rapid molecular tests at the lower tier of the TB diagnostics network, consequently confining TB diagnosis to smear microscopy. Truenat technology offers significant advantages over existing technologies. The Ministry of Health (MoH), through NTLP, aligned with WHO recommendations by adopting and integrating the Truenat platform into the TB diagnostic network. In May 2023, the CTRL facilitated the first phase of integrating Truenat technology for TB diagnosis in 30 sites across 24 regions. Additionally, the CTRL received 7 Truenat machines from the Ifakara Health Institute (IHI) making a total of 37 machines. By the end of 2023 a total of 2,879 tests were conducted. (Figure 5).
Figure 25: TrueNat tests in 2023
To ensure appropriate electronic data collection, CTRL has kept on with the mWRDs digital connectivity scale up endeavours. Among the 306 sites, 289 (94%) had been linked with GxAlert/Aspect system software and the four Xpert MTB/XDR machines have only been linked to the DHIS2-ETL system and they all upload data to the national servers (Figure 26).
Figure 26: Scale up of GeneXpert and GxAlert from 2015 to 2023
