External Quality Assessment for Tuberculosis Diagnosis and Drug Resistance in the European Union: A Five Year Multicentre Implementation Study

Abstract

Background: External quality assurance (EQA) systems are essential to ensure accurate diagnosis of TB and drug-resistant TB. The implementation of EQA through organising regular EQA rounds and identification of training needs is one of the key activities of the European TB reference laboratory network (ERLTB-Net). The aim of this study was to analyse the results of the EQA rounds in a systematic manner and to identify potential benefits as well as common problems encountered by the participants.

Methods: The ERLTB-Net developed seven EQA modules to test laboratories' proficiency for TB detection and drug susceptibility testing using both conventional and rapid molecular tools. All National TB Reference laboratories in the European Union and European Economic Area (EU/EEA) Member States were invited to participate in the EQA scheme.

Results: A total of 32 National TB Reference laboratories participated in six EQA rounds conducted in 2010-2014. The participation rate ranged from 52.9% - 94.1% over different modules and rounds. Overall, laboratories demonstrated very good proficiency proving their ability to diagnose TB and drug-resistant TB with high accuracy in a timely manner. A small number of laboratories encountered problems with identification of specific Non-tuberculous Mycobacteria (NTMs) (N = 5) and drug susceptibility testing to Pyrazinamide, Amikacin, Capreomycin, and Ethambutol (N = 4).

Conclusions: The European TB Reference laboratories showed a steady and high level of performance in the six EQA rounds. A network such as ERLTB-Net can be instrumental in developing and implementing EQA and in establishing collaboration between laboratories to improve the diagnosis of TB in the EU/EEA.

Fig 1. Laboratories participating in EQA rounds and modules.

Fig 2. Results of proficiency testing in rounds 1 to 6 by module.

Fig 3. Smear microscopy error rates for microscopy diagnosis by Ziehl-Neelsen, auramine or Kinyoun methods.

Fig 4. Error rates for tuberculosis drug susceptibility testing by phenotypic tools and molecular tools grouped by individual drugs.

INH, isoniazid; RIF, Rifampicin; EMB, Ethambutol; PZA, pyrazinamide; STR, streptomycin; FQ, fluoroquinolones; AMK, amikacin; CAP, capreomycin; KAN, Kanamycin; AG/CP, aminoglycosides/cyclic peptides. DST, Drug Susceptibility Testing. For molecular tests, a combined resistance to injectable drugs (“AG/CP”) was reported instead of individual resistance to AMK, CAP, and KAN.