External quality assessment for molecular detection of Bordetella pertussis in European laboratories

Although the PCR for the detection of Bordetella pertussis is routinely performed in diagnostic laboratories, no quality assessment program has so far been described. We report on the results obtained with two external quality assessment proficiency panels sent to European laboratories. The first proficiency panel contained a series of dilutions of three previously characterized B. pertussis clinical isolates and two negative controls. No false-positive results were reported by six laboratories providing seven data sets. The reported limits of detection of the three B. pertussis strains varied between 4 and 4,000, 9 and 9,000, and 3 and 30,000 CFU/ml, respectively. The second proficiency panel, composed of a series of dilutions of reference strains of B. pertussis, B. holmesii, B. hinzii, and B. bronchiseptica, as well as negative controls, was sent to nine laboratories. One laboratory reported a negative result for a sample and reported a B. parapertussis-positive sample to be positive for B. pertussis. By using the B. pertussis-specific target gene pertactin, one laboratory detected B. pertussis with 100% specificity. All other laboratories, which used IS481-based assays, reported positive results for the samples containing B. holmesii and B. bronchiseptica, species that have occasionally been recovered from human respiratory samples. These data show that the choice of the target gene is particularly critical for the species specificity of B. pertussis PCR assays.     

The United Kingdom national microbiological quality assessment scheme.

A comprehensive microbiological quality assessment scheme for the benefit of all clinical microbiological laboratories in the United Kingdom was established in 1974. The main emphasis of the scheme has been on the supply of simulated clinical material for proficiency testing. Of 494 laboratories currently participating in the scheme, 84 are abroad and over 500 specimens have been distributed between 1974 and 1980. A wide variety of specimens are issued. These include specimens for: general bacteriology including isolation, sensitivity testing and serology; mycobacterial bacteriology; syphilis serology; virus isolation; general viral serology; rubella serology; hepatitis B antigen detection; electron microscopy; mycology; parasitology; antibiotic assay; public health specimens including milk and water. Laboratories are requested to examine the specimens using their routine procedures and report their results to the Microbiological Quality Control Laboratory (MQCL). The reports are analysed at MQCL and the summarised results of each distribution are sent to all participants. Each participant receives details of his individual performance on current specimens and an analysis of the previous 6 months, cumulative performance. The performance of all laboratories is reviewed twice yearly and laboratories with results significantly worse than those of their peers are offered the opportunity to seek advice and help from a National Advisory Panel of their professional colleagues. The Scheme is confidential and its main role is educational.     

Mycology quality assessment: United Kingdom national scheme.

A mycology quality assessment scheme introduced in 1986 was assessed: 289 laboratories participated in the scheme, and six distributions, each containing four specimens, were made. Levels of performance varied considerably among participating laboratories: performance was highest with the commoner organisms distributed, but some laboratories, encouragingly, achieved a consistently high level of species identification. A questionnaire distributed to participants showed that a wide range of methods are commonly used, some of which are contrary to good practice. As the scheme continues, selection of organisms considered to be relevant and of use to participants will become difficult.     

External quality assessment with reference to the certification/accreditation of medical laboratories

Since ISO 15189 (Medical Laboratories-Particular requirements for quality and competence) was published in February 2003, interest in the accreditation of medical laboratories has increased in Japan. Under such conditions, the JCCLS (Japanese Committee for Clinical Laboratory Standards) and the JAB (Japan Accreditation Board for Conformity Assessment) are promoting a project on an accreditation program for medical laboratories in Japan. The JAB is planning to start their pilot inspections from October, 2004. In this paper, an external quality assessment scheme in Japan on proficiency testing for the accreditation of clinical laboratories is described.     

A comparative survey of the results of analyses of blood serum in clinical chemistry laboratories in the United Kingdom

Since July 1969, portions of the same blood serum have been dispatched to clinical chemistry laboratories in the United Kingdom at 14-day intervals. The results of each serum survey were reported to each of the 390 participants within 11 days of their originally receiving the specimen.During the first 18 months of the survey no overall improvement in the results was seen. Therefore a summary of each laboratory's ability consistently to produce results close to the mean of the method used was calculated and reported as a single figure, the variance index, and sent to all participants at regular intervals together with a histogram distribution of the variance indices of other participants. The subsequent improvement in the overall results is described.     

Detection of ampicillin resistant Haemophilus influenzae in United Kingdom laboratories.

Susceptibility of Haemophilus influenzae clinical isolates to ampicillin reported by 23 laboratories, using a variety of methods, was compared with results obtained following retesting at The London Hospital Medical College. Beta lactamase production was not detected on initial isolation in 25 of 157 isolates (16%) found to be positive on retest. One hundred beta lactamase negative isolates, which gave reduced zone diameters (less than 20 mm) around 2 micrograms discs and required 1-64 mg/l ampicillin for inhibition, were detected at The London Hospital. Eighty five of these had been reported as sensitive to ampicillin by the laboratories of origin. Many of these 100 isolates showed reduced susceptibility to other beta lactam antibiotics. Accurate detection of non-enzymic reduced susceptibility to ampicillin may emerge as an important guide to the likely sensitivity of H influenzae isolates to the enzyme stable beta lactams.     

External quality assessment of molecular typing of Staphylococcus aureus isolates by a network of laboratories

A network of laboratories designated Centres for Molecular Diagnosis was funded in 2000 by Belgian National Health Insurance to provide clinically relevant molecular diagnostic tests. These included typing of nosocomial pathogens as a service to local hospital infection control programs. Two external quality assessment (EQA) surveys were performed in 2001 and 2003 to evaluate the proficiencies of the laboratories at Staphylococcus aureus typing. EQA panels included S. aureus isolates with either indistinguishable, clonally related, or unrelated pulsed-field gel electrophoresis (PFGE) patterns. A hypothetical hospital outbreak problem was also submitted for analysis. Typeability, reproducibility, discrimination (D) index, and epidemiological concordance were evaluated. Ten centers participated in each survey. Seven centers performed PFGE analysis, while others used repetitive-element or randomly amplified polymorphic DNA PCR, amplified fragment length polymorphism, or spa typing. Full typeability (100%) was achieved by all centers, and all but one showed 100% reproducibility. Discrimination was appropriate (D index, >or=96%) for centers performing PFGE analysis but not for all those using other methods (D index range, 72% to 97%). Correct answers to the epidemiological questions were provided by 7/10 and 10/10 centers in 2001 and 2003, respectively. Individual feedback of results was provided to each center together with specific technical recommendations for improving performance. Our findings indicate that surveys of lab proficiency are useful for validation and optimization of molecular typing services to local hospital infection control programs.     

A survey of infections in United Kingdom laboratories, 1994-1995

AIMS: To identify the number and type of infections occurring in United Kingdom clinical laboratories during 1994 and 1995, following similar surveys covering 1970 to 1989. METHODS: A retrospective questionnaire survey was undertaken of 397 responding UK clinical laboratories covering 1994 and 1995. A follow up telephone survey was undertaken with each of the laboratories from which a questionnaire had been received indicating a possible or probable laboratory acquired infection during 1994 or 1995. RESULTS: Questionnaires were sent to 659 laboratories or organisations which were thought to have laboratories, of which 557 responded (response rate of 84.5%). Of these, only 397 were from organisations with laboratories. Over 55,000 person-years of occupational exposure were covered, and only nine cases identified, giving an infection incidence rate overall of 16.2/100,000 person-years, compared with 82.7 infections/100,000 person-years found in a similar survey covering 1988 and 1989, reported previously. Infections were commonest in females, in relatively young staff, in microbiology laboratory workers, and in scientific/technical employees. Gastrointestinal infections predominated, particularly shigellosis, but few specific aetiological factors relating to working practices were identified. No hepatitis B cases were reported. CONCLUSIONS: The small number of cases identified indicates high standards of infection control, though there is still room for improvement. Periodic studies of this kind are not adequate for comprehensive monitoring of the incidence of laboratory acquired infections. That will require the introduction of a routine, active surveillance programme or prospective survey which has the support and commitment of the laboratories themselves.     

Total quality management in clinical virology laboratories

The diagnostic laboratories in India are progressively promoting higher standards and are moving towards accreditation and international acceptance. Hence, the concept of "Quality" will need to be understood and implemented. Total quality management (TQM) in a laboratory is an integrated program involving all laboratory staff and management. TQM is a framework to operate and it is aiming for integration, consistency, increase in efficiency and a continuous drive for improvement. A well structured clinical virology service will include serology setup, cell culture facility and capacity for molecular diagnosis. The quality of results from the laboratory is significantly influenced by many pre-analytical and post-analytical factors which needed attention. The end goal of the TQM should be to provide the best care possible for the patient.     

Accuracy of methods used for susceptibility testing of Haemophilus influenzae in United Kingdom laboratories

Antibiotic susceptibility test reports on 1841 strains of Haemophilus influenzae from 25 microbiology laboratories were compared with results obtained with the same strains at The London Hospital Medical College. Of strains found to be sensitive to the antibiotics tested, 0.5% were reported as tetracycline-resistant, 1.6% as ampicillin-resistant, and 6.2% as trimethoprim-resistant. Of strains found to be resistant to these antibiotics, 37% were reported as tetracycline-sensitive, 27% as ampicillin-sensitive, and 66.7% as trimethoprim-sensitive. Factors found to be of significance in improving accuracy of sensitivity reporting included use of chromogenic cephalosporin and low-content antibiotic discs for detection of ampicillin resistance, and use of lysed blood agar rather than chocolated blood agar to detect trimethoprim sensitivity.     

A quality assessment survey of SNP genotyping laboratories

To survey the quality of SNP genotyping, a joint Nordic quality assessment (QA) round was organized between 11 laboratories in the Nordic and Baltic countries. The QA round involved blinded genotyping of 47 DNA samples for 18 or six randomly selected SNPs. The methods used by the participating laboratories included all major platforms for small- to medium-size SNP genotyping. The laboratories used their standard procedures for SNP assay design, genotyping, and quality control. Based on the joint results from all laboratories, a consensus genotype for each DNA sample and SNP was determined by the coordinator of the survey, and the results from each laboratory were compared to this genotype. The overall genotyping accuracy achieved in the survey was excellent. Six laboratories delivered genotype data that were in full agreement with the consensus genotype. The average accuracy per SNP varied from 99.1 to 100% between the laboratories, and it was frequently 100% for the majority of the assays for which SNP genotypes were reported. Lessons from the survey are that special attention should be given to the quality of the DNA samples prior to genotyping, and that a conservative approach for calling the genotypes should be used to achieve a high accuracy.     

External quality assurance and assessment in immunocytochemistry

A quality assurance scheme for immunocytochemistry was started in 1984. There are currently 140 participating laboratories, most of which have shown considerable improvement in their results since joining the scheme. In our experience the supplier of the primary antibody does not affect the quality of the results; the sensitivity of the method used and the experience of the staff carrying out the technique are the most important factors. Participation in a scheme such as this enables laboratories to have their results compared with others and to share problems.     

External quality assessment of pertussis serology in Germany

The purpose of this investigation was to test the performance of pertussis serology in diagnostic laboratories. The World Health Organization (WHO) Reference Reagent (06/142) and a sample with a low level of antibodies were sent to 200 participants of an external quality assessment (EQA) programme in Germany. The results were reported qualitatively and quantitatively, and were converted into IU/ml when possible. A total of 183 participants reported results. IgG, IgA and IgM enzyme-linked immunosorbent assays (ELISAs) with mixed antigens were used by 111, 110 and 113 participants, respectively, and 69 and 44 participants used IgG and IgA ELISAs with purified pertussis toxin (PT), respectively. IgG, IgA and IgM immunoblots were employed by 62, 63 and 11 participants, respectively. Most tests could distinguish between the positive and negative samples, but quantitative results were reported partly in non-comparable units. Only 37 % of participants used ELISAs that gave results comparable to the expected values in IU/ml and that could be interpreted according to published recommendations.     

vCJD and blood transfusion: risk assessment in the United Kingdom.

The risk of vCJD transmission via blood transfusion depends on potential levels of infectivity, recipients' exposure to infected donors and individual susceptibility. On infectivity, SEAC (the UK's main scientific advisory committee on TSEs), has published an updated position statement. Based on animal models, this suggests that infectivity is split roughly equally between leucocytes and plasma, with negligible levels directly associated with red cells or platelets. Risk assessments are now therefore based on the amounts of plasma and leucocytes within each component as transfused. Recipients' exposure to infection depends critically on the prevalence of infection in the population. This remains unknown, so a range of assumptions must still be considered. A further consideration is the likelihood of any infected donors' blood being infective. Those infected in the primary outbreak will now have been incubating vCJD for 10-25 years. Current thinking is that blood may be more infective later in the incubation period. This reinforces the case for a precautionary approach to transmission risks, despite the small number of incidents seen so far. Exposure will also depend on how many donors contributed components to a given individual. Recent work has shown that more patients receive large numbers of units than previously thought. These highly-transfused patients are a particular cause for concern. The current precautionary assumption is of all recipients being susceptible to infection by transfusion, though incubation periods may differ markedly.