Random Blinded ReChecking [RBRC] Process at DTC

Random Blinded Rechecking (RBRC) is the process of re-reading a statistically valid sample of routine slides from a designated microscopy centre (DMC) based on lot quality assurance strategy (LQAS) in a blinded manner to assess the laboratory performance.

RBRC Process

• The district TB officer (DTO) sends information to all senior TB lab supervisors (STLS) of the district on the number of slides to be collected every month from each DMC
• The STLS then selects the required number of slides from the TB Laboratory Register and marks the RBRC selected slides in the laboratory register with a circle
• The laboratory technician (LT) fills out Annexure B (Figure 1) for the selected slides
• LT seals the filled Annexure B in an envelope and marks the slide box with the Serial No. of slides, name of the DMC and TB unit (TU), month and year
• The STLS hands over sealed envelopes and the slide box to the DTO

Figure 1: Annexure B for Blinded Rechecking of DMC Slides (RNTCP Laboratory Network Guidelines)

• The DTO with the help of the statistical assistant (SA) removes all the identifying attributes of the selected slides (including the test results). This process is called Blinding.
• Blinded re-examination of selected slides is done by the STLS of another TB Unit (TU) within the respective district. The STLS (controllers) must have demonstrated proficiency with the Ziehl-Neelsen (ZN) staining and reading method (as seen by panel testing done by Intermediate Reference Laboratory (IRL)).
• Smears may be evaluated for specimen quality (sputum versus saliva), appropriate size and thickness, and quality of staining (as per Annexure C, Figure 2).

Figure 2: Worksheet for Blinded Rechecking of DMC Slides as per Annexure C (RNTCP Laboratory Network Guidelines)

• Problems detected by the controller are noted on the form, as this information may be very useful to supervisors responsible for providing feedback to the peripheral technicians, assessing possible reasons for high false positive or false negative results, and implementing plans for retraining and corrective action. 
• The DTO with the help of the statistical assistant compares the results provided by the STLS against the original results provided by the LT. This process is called Unblinding.
• The discrepant slides are sent for umpire (second controller) reading.
• All discrepant slides are re-stained and re-examined by the second controller, as there is likelihood of fading of carbol fuchsin. This rechecking of discordant slides by a second controller also acts to evaluate the performance of the first controllers.

Feedback after RBRC

• Regular and timely feedback to the DMC is essential to improve performance
• Feedback and remedial actions are provided at the end of each sampling period i.e., completion of rechecking of the annual sample
• Also, feedback is given on a monthly basis to the respective DMCs using the form in Annexure D (Figure 3) during the monthly on-site evaluation visit by the STLS responsible for the respective DMC
• Feedback includes the return of slides with discordant results to be re-read by the original LT of the respective DMC
• Potential sources of errors are investigated during the on-site evaluation visit
• Appropriate corrective actions and/or remedial training are provided within one month

Figure 3: Quality Assurance Report on Sputum Microscopy as per Annexure D (RNTCP Laboratory Network Guidelines)

Resources

RNTCP Laboratory Network Guidelines

Assessment