A national audit of the laboratory diagnosis of tuberculosis and other mycobacterial diseases within the United Kingdom.

Abstract

In order to audit United Kingdom laboratory diagnostic and reference services including novel molecular methods for tuberculosis, a questionnaire was sent to laboratories submitting specimens to the PHLS Mycobacterium Reference Unit (MRU) and regional centres and to the Scottish Mycobacteria Reference Laboratory (SMRL) in 1996-7. Nationally, 67.2% of laboratories responded. Most UK laboratories were fully or conditionally CPA accredited and take part in the NEQAS proficiency scheme. On average only 3.3% of primary samples submitted for mycobacterial diagnosis in 1995 produced a mycobacterial culture from approximately half as many patients (that is, a mean of 1488 specimens producing 49 isolates from 23 patients). Potentially over 380 000 specimens are processed for mycobacteria in the UK each year. The majority of laboratories use 4% NaOH ± NALC for specimen decontamination. Culture on solid media was used by most laboratories and 62.9% also use liquid media. Most laboratories incubated cultures for eight weeks. Few laboratories use molecular diagnostic methods. Laboratories were most likely to use molecular methods for diagnosing tuberculous meningitis and for specimens from immunocompromised patients, although usage was strongly influenced by cost. Within England and Wales 43.9% (47/107) and 56% (61/109) of laboratories wanted a rapid service for rifampicin resistance detection in M tuberculosis from immunocompetent and immunocompromised patients, respectively. In regard to a tuberculous meningitis service, 80.5% (43/ 112) and 84.3% (102/121) of laboratories wanted this service for immunocompetent and immunocompromised patients, respectively. The quality of reference services was rated as "very good"/"good" by 85.6% of respondents nationally. Rapid molecular amplification diagnostic services were established at the PHLS MRU for rifampicin drug resistance detection nationally and for tuberculous meningitis at the MRU. The PHLS Mycobacterium Reference Unit and Regional Centre for Mycobacteriology (MRU), London, PHLS regional centres for mycobacteriology (RCM) at Birmingham, CardiV, and Newcastle, and the Mycobacteria Reference Laboratory, Scotland (SMRL) receive, identify, and perform drug susceptibility testing on over 95% of all mycobacteria cultured by hospital laboratories within the mainland United Kingdom. They also operate as diagnostic centres for their associated (and some additional) NHS Trusts. MethodsBetween August 1996 and May 1997, client laboratories of the PHLS MRU, the regional centres for mycobacteriology, and the SMRL were sent a detailed questionnaire. Questionnaires were prepared in EpiInfo 6 (Centres for Disease Control, Atlanta, Georgia, USA) at the MRU and piloted at two sites initially. The questionnaires built on earlier audits conducted by the SMRL and the Birmingham Regional Centre for Mycobacteriology. Replies were analysed in either EpiInfo 6 or Microsoft Excel.The questionnaire requested information on the type of laboratory and containment facilities available, the number...

A clinical, microbiological and economic analysis of a national service for the rapid molecular diagnosis of tuberculosis and rifampicin resistance in Mycobacterium tuberculosis

“…There are clear benefits in also determining rifampicin resistance and a survey of UK clinical laboratories indicated that a national service to determine resistance in smear-positive sputum samples was needed [28].…”

“…Nevertheless, in the UK, 380 000 specimens are taken annually from patients in whom tuberculosis is a differential diagnosis, but they yield only c. 3500 bacteriologically proven cases [10,28]. Therefore, use of these tests for screening would be inappropriate, but it would be appropriate to apply these tests to infectious patients with risk factors for drug resistance including contact with MDRTB cases, patients with prior tuberculosis and those born overseas in high incidence countries, as well as at risk immunocompromised individuals.…”

A systematic review of rapid diagnostic tests for the detection of tuberculosis infection

“…134 In the normal course of diagnosis, hospitals perform microscopy and culture (usually on to solid media but increasingly using liquid culture media); over 95% of hospitals then refer these cultures to the reference unit for identification and drug susceptibility testing. In the more streamlined model, hospitals send AFBpositive sputum samples directly to the reference laboratory for rapid culture.…”

Cost-Effectiveness Analysis of the Gen-Probe Amplified Mycobacterium Tuberculosis Direct Test as Used Routinely on Smear-Positive Respiratory Specimens

“…For smear-positive respiratory specimens, the sensitivity of the enhanced MTD has been reported between 91.7% (17) and 100% (2,6,11,20), with specificity between 99.6% (6) and 100% (2,11,19). Despite such demonstrated high validity, the routine implementation of nucleic acid amplification tests in clinical settings has been slow, due in large part to concerns of their high cost, previously estimated at $50 to $100 per test in most laboratories (10). To determine whether this cost may be offset by savings in the form of isolation room and medication expense, we conducted a costeffectiveness analysis of the routine use of MTD during the evaluation of patients suspected of having pulmonary TB at a large urban hospital in the mid-Atlantic United States.…”