The definite diagnosis of tuberculosis demands that M. tuberculosis be recovered on culture media and identified using differential in vitro tests. Hence using laboratory standards is an important aspect of ensuring quality processes in all aspects of MGIT DST. 

These include the following:

1. Standard laboratory biosafety measures as applicable to TB containment laboratories for handling culture isolated and performing DST

2. Trained staff to use standard operating procedures for equipment and laboratory methods 

MGIT DST Quality Control

Quality control of MGIT DST is critical to laboratory testing, as it ensures the accuracy and consistency of the test processes and the results reported. 

Frequency: 

It is important to perform quality control (QC) of drug susceptibility testing periodically. This testing must be performed:

• For each new batch of reagents (MGIT drug kits, other drugs, media, etc.) 

Retesting MGIT DST Results

The cause for the unexpected/false profile of DST isolate can be due to various reasons that reflect quality aspects of the laboratory as well as the characteristic of the MGIT growth. The following need to be looked into as cause for unexpected/false profiles of DST isolate:

1. Laboratory procedures:

Troubleshooting False Resistant DST Results

The common reasons for getting false resistant DST results, along with their corrective actions, are given in the table below:

Troubleshooting False Susceptible DST Results

The common reasons for getting false susceptible DST results, along with their corrective actions, are given in the table below:

Troubleshooting Non-interpretable DST

Error or indeterminate DST results are reported when certain conditions occur that may affect the test. These results are designated by the alphabet ‘X’ followed by a code. Following two types of such errors are encountered:

MGIT 960 DST Inoculum Troubleshooting

MGIT 960 DST Equipment and Reagents Troubleshooting

If the BACTEC™ MGIT™ instrument malfunctions or operates unusually in any way, an error message will appear on the instrument. These messages are in numerical order, along with possible causes of the message and corrective actions are listed below.

Table: Errors encountered during the operation of the BACTEC™ MGIT™ instrument and their corrective actions