[雙語翻譯]--醫(yī)學(xué)外文翻譯--結(jié)核分枝桿菌檢測（英文）

1、244 Arch Pathol Lab Med—Vol 132, February 2008 Mycobacterium tuberculosis, Genetic—El-Sayed Zaki Samir Abou-El Hassan, MD● Context.—Diagnostic detection of tuberculosis (TB) has improved considerably. Available, standar

2、dized, nucleic acid–based amplification techniques have been shown to yield reliable results within 4 to 7 hours of sample pro- cessing. Objective.—To study the diagnostic performance of Gen-Probe’s technique for direct

3、detection of Mycobacte- rium tuberculosis in comparison with BACTEC 460 TB cul- ture for both positive and negative Ziehl-Neelsen smears in Egyptian children at risk for TB infection. Design.—We prospectively evaluated 5

4、0 children from families with a positive history of TB. All patients were re- ferred from outpatient clinics of the Mansoura University Children’s Hospital, Egypt. The children had a positive tu- berculin skin test with

5、an induration diameter of more than 10 mm and had scars from a bacille Calmette-Gue ´rin vac- cination within the past 2 years. Three consecutive sputum samples were taken from each patient. The samples wereexamined

6、 to detect M tuberculosis by means of the Gen- Probe technique, direct smear microscopy, and bacterial culture by BACTEC 460 TB. Results.—Of the 50 cases, 30 (60%) had sputum samples that were positive for TB by BACTEC 4

7、60 TB culture, and 29 cases (58%) were positive by the Gen-Probe technique. Sensitivity and specificity of Ziehl-Neelsen smears was 83.3% and 100%, respectively, with overall accuracy of 90%. Sensitivity and specificity

8、of the Gen-Probe tech- nique were 96.7% and 100%, respectively, with overall accuracy of 98%. Conclusions.—The results of this study suggest that the Gen-Probe technique is an accurate method for rapid de- tection of M t

9、uberculosis complexes in respiratory samples from children at risk for TB. It can be used for diagnosis of smear-negative cases that are suspect for TB. (Arch Pathol Lab Med. 2008;132:244–247)C hildhood tuberculosis (TB)

10、 has its highest incidence among children in contact with bacilliferous adults.1,2The present study was motivated by the increase in the number of TB cases that are being observed in children. Traditional laboratory diag

11、nosis of mycobacterial infec- tions by culture usually requires 2 to 8 weeks. The recent increase in new cases of TB has shown the need for rapid, specific, diagnostic assays for Mycobacterium tuberculosis.3With the deve

12、lopment of novel techniques in molecular biology, this delay might be shortened. Most of the nucleic acid amplification assays are rapid and specific.4Despite their theoretical ability to detect even a single mycobacteri

13、al cell, nucleic acid amplification tests (NAATs) are not sufficiently reliable to replace conven- tional diagnostic methods for detecting TB. Inherent test characteristics and errors in testing procedures may ac-Accepte

14、d for publication September 17, 2007. From the Departments of Clinical Pathology (Dr El-Sayed Zaki) and Pediatrics (Dr Abou-El Hassan), Faculty of Medicine, Mansoura Uni- versity-Egypt. The authors have no relevant finan

15、cial interest in the products or companies described in this article. Reprints: Maysaa El-Sayed Zaki, MD, Egypt-Mansoura University, Faculty of Medicine, Department of Pathology, Mansoura 65 Egypt (e-mail: may?s65@hotmai

16、l.com).count for their inaccuracy.5 Furthermore, the presence in respiratory secretions of enzymes capable of inhibiting amplification reactions accounts for an additional 3% to 25% of false-negative results.6On the othe

17、r hand, false-positive results arise most of- ten from contamination of negative samples with either organisms or target DNA from samples containing large numbers of mycobacteria or from amplicons contaminat- ing the lab

18、oratory room.5,6To overcome these problems, automated commercial systems were developed that were made more robust by the use of standardized procedures and reagents for sam- ple processing, amplification, and detection.

19、 Various automated systems, based on amplification and detection techniques, have been devised for the detection of M tuberculosis in clinical samples. The systems include the polymerase chain reaction–based COBAS AMPLIC

20、OR Mycobacterium system (Roche Diagnostics, Basel, Swit- zerland)7; the transcription-mediated, amplification-based Amplified Mycobacterium Tuberculosis Direct Test (AMTD; Gen-Probe, Inc, San Diego, Calif)8; the strand d

21、is- placement amplification-based BD ProbeTec ET system (Becton Dickinson and Company, Franklin Lakes, NJ)9; and the ligase chain reaction–based Abbott LCx M tuber- culosis assay system (Abbott Laboratories, North Chicag

22、o,246 Arch Pathol Lab Med—Vol 132, February 2008 Mycobacterium tuberculosis, Genetic—El-Sayed Zaki however, the latter lacks sensitivity and is unable to distinguish tubercle bacilli from other mycobacteria.22For result

23、s of AMTD compared with culture, 29 cases were Gen-Probe positive and culture positive, and 1 case was negative by Gen-Probe and culture positive. Four samples of AFB smears were positive by culture and Gen- Probe. Gener

24、ally, differences between cutoff values of positive and negative controls and specimens were broad enough to permit easy discrimination. Negative results obtained by AMTD for culture-positive specimens may be ex- plained

25、 by unequal distribution of a small number of my- cobacteria.23 It is clear that the Gen-Probe technique can be used for the confirmation of TB in a percentage of thoseproviding AFB samples. A similar conclusion was repo

26、rt- ed by Greco et al23 for most automated systems. The impact of the NAATs on patient outcome varies based on the result of the AFB smear. In smear-positive patients, public health and hospital infection-control re- sou

27、rces are predominantly affected. The potential for in- fluencing patient outcome is much greater when the AFB smear is negative. In smear-negative patients, the NAAT could provide more rapid diagnosis of TB and subsequen

28、t initiation of therapy; this would eliminate the need for invasive diagnostic procedures, which are costly and pose an added risk to the patient and allow for earlier discharge of hospitalized patients.25Therefore, in a

29、 developing country such as Egypt, we can restore the use of NAAT in suspect cases with AFB samples to decrease the cost of diagnosis. The cost of cul- ture versus smear examinations is around $25, whereas the cost of th

30、e Gen-Probe per case is around $50. The data presented here show the outstanding sensitiv- ity and specificity of the Gen-Probe test. Sensitivity of the Gen-Probe test was 96.7%, specificity was 100%, positive predictive

31、 value was 100%, negative predictive value was 95.2%, and overall accuracy was 98%. Sensitivity was 80% for smear-negative samples. Wang and Tay25 similarly re- ported that sensitivity of AMTD was 98.4%, specificity was

32、100%, and positive predictive value was 100%. In the present study, the Gen-Probe test proved to be valuable as a rapid and accurate method for diagnosis of pulmonary TB in children at risk for TB. The results can be ava

33、ilable within 4 hours, whereas the culture results may be obtained within 14 days. We cannot depend on ZN alone as a rapid method because of its reduced sen- sitivity. There are numerous difficulties in controlling TB co

34、n- tacts in the Egyptian scenario. Although official proce- dures recommend that all contacts of TB patients be screened, the lack of diagnostic strategies prevents the ear- ly diagnosis of a large number of TB cases, th

35、ereby in- creasing disease transmission. We can suggest the use of combinations of simple tests, such as chest x-ray and ZN stain, for children at risk for TB. For those with negative results, we can proceed to culture o

36、r NAAT, according to the situation. The results of this study suggest that the Gen-Probe test is an accurate method for rapid detection of M tuberculosis complexes in respiratory samples from children at risk for TB. It

37、can be used for smear-negative cases that are sus- pect for TB.References1. Alves R, Sant’anna CC, Cunha AJL. A Epidemiologia da tuberculose infantil na cidade do Rio de Janeiro, RJ. Rev Sau ´de Pu ´blica. 2000

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42、rium growth indicator tube testing in conjunction with the AccuProbe or the AMPLICOR-PCR assay for detecting and identifying mycobacteria from sputum samples. J Clin Microbiol. 1997;35:2022–2025. 8. Ichiyama S, Iinuma Y,