Evaluation of sputum smear microscopy in the National Tuberculosis Control Programme in the north of Vietnam.

OBJECTIVE: To assess the yield of sputum smear microscopy and sex differences in the National Tuberculosis Control Programme in the north of Vietnam. METHODS: Review of registers of 30 randomly selected laboratories (26 district, 4 provincial level). RESULTS: The average daily workload per technician was 4.4 examinations in district and 5.3 examinations in provincial laboratories. To find one smear-positive case, 9.7 suspects were examined and 29.3 smears done. The smear-positive rate (mean 10.3%) was higher among men (11.6%) than among women (8.4%, P < 0.001). There were more men than women among tuberculosis (TB) suspects (male:female ratio 1.36, 95%CI 1.19-1.54), but even more so among smear-positive patients (1.89, 95%CI 1.64-2.14), irrespective of specimen quality and number of smears examined. Three smears were examined for 18,055 suspects (61.7%). The incremental gain was 33.5% and 4.9% for the second and third smear examination, respectively; 186 (95%CI 160-221) smears needed to be examined to find one additional case of TB with a third serial examination. CONCLUSION: The diagnostic process seemed generally efficient. The male:female ratios suggest higher TB incidence in men rather than lower access to TB facilities for women. The third smear examination could be omitted.     

Efficiency of serial smear examinations in excluding sputum smear-positive tuberculosis.

SETTING: This study determined the number of slides required to identify one additional case of sputum smear-positive tuberculosis (TB) from the third smear. The study hypothesis was that not more than 100 and 75 slides, respectively, in Mongolia and Zimbabwe, need to be examined to find one additional case of TB with a third serial diagnostic sputum smear examination. METHODS: In a retrospective, record-based study, data were abstracted from TB laboratory registers from all 31 laboratories in Mongolia and 23 randomly selected laboratories in Zimbabwe using a uniform EpiData collection instrument. RESULTS: A total of 52,909 records of examinees were available. In Mongolia, of 15 103 suspects, 1717 (11.4%) were positive. Of these, 0.7% were positive for the first time on the third smear examination. In Zimbabwe, of 25 693 suspects, 3452 (13.4%) were positive and 4.5% were positive only on the third smear examination. The expected number of slides required to detect one additional case on the third examination was 1153.3 for Mongolia and 132.6 for Zimbabwe. CONCLUSIONS: The requirement of routine examination of three serial smears before declaring a suspect as a 'non-case' (of sputum smear-positive TB) will need to be reviewed in both Mongolia and Zimbabwe.     

A method to determine the utility of the third diagnostic and the second follow-up sputum smear examinations to diagnose tuberculosis cases and failures.

SETTING: Forty-two laboratories in four countries. OBJECTIVE: To determine the number of sputum smear examinations required to identify one additional case of tuberculosis from a third serial diagnostic smear or one additional treatment failure from a second serial follow-up smear. MATERIAL AND METHODS: Country-specific prevalence of new cases and failures among 59 665 examinees were determined, as well as the incremental yield from serial smears. The reciprocal value of the product of the prevalence of cases or failures and the respective incremental yield from the last serial smear provided the number of slides that have to be examined to identify one additional case or failure. RESULTS: The expected prevalence of cases among suspects ranged from 5.4% to 32.8%; the incremental yield from a third serial smear ranged from 0.7% to 7.2%. Between 122.7 and 796.3 smears were required to identify one additional case with the third serial smear. The prevalence of failures among follow-up examinees ranged from 1.0% to 2.5%; the incremental yield from the second follow-up serial smear ranged from 4.5% to 26.9%. Between 164.8 and 2133.4 slides were required to identify one additional failure with the second serial smear. CONCLUSION: The utility of serial smears can be rationally determined by careful review of program data.     

An incremental cost-effectiveness analysis of the first, second and third sputum examination in the diagnosis of pulmonary tuberculosis.

SETTING: St. Francis Hospital in Katete District, Eastern Province, Zambia. OBJECTIVE: To compare the incremental cost-effectiveness of examining serial sputum smears for screening suspects for pulmonary tuberculosis at a rural district hospital in Zambia. DESIGN: An incremental cost-effectiveness analysis of serial sputum smear examinations for diagnosing pulmonary tuberculosis based on laboratory results collected during 1997 and 1998 in a rural district hospital in Zambia. The cost analysis took a health service provider perspective, and used the ingredients approach. The cost-effectiveness is expressed in terms of the incremental cost per tuberculosis case diagnosed. Relevant information was obtained from various sources, including administrative records, interviews and direct observation. RESULTS: Of a total of 166 acid-fast bacilli positive suspects who had three sputum smears examined sequentially, 128 (77.1%) were found on the first smear, a further 25 (15%) on the second smear and 13 (7.9%) additional cases were identified on the third smear. The economic analysis shows that the incremental cost of performing a third test, having already done two, increases rapidly with only a small gain in terms of additional cases of tuberculosis identified. CONCLUSION: A policy of examining two samples should be considered in resource-poor settings, if the remaining steps of the national diagnostic algorithm can be adhered to with respect to smear-negative suspects.     

Sputum smear-positive tuberculosis: empiric evidence challenges the need for confirmatory smears.

OBJECTIVE: To determine the frequency of single scanty or positive sputum smear results and its impact on the surveillance definition of sputum smear-positive tuberculosis (TB). SETTING: Moldova, Mongolia, Uganda and Zimbabwe. METHODS: A representative sample of laboratories was selected in each country. Data were double-entered and discordances resolved by rechecking the register. RESULTS: The dataset comprised 128808 examinees with valid information from 23 laboratories in Moldova, all 31 in Mongolia, 30 in Uganda and 23 in Zimbabwe, each covering at least one calendar year. The reason for the examination was diagnostic for 89362, of which 15.2% (n = 13577) were defined as laboratory cases with at least one bacillus on at least one examination. Cases were confirmed by another examination in 72.6% (n = 9861). Of the 9014 cases who had a full set of three examinations, confirmation was obtained in 92.4% (n = 8325). CONCLUSION: One quarter of laboratory cases had no confirmatory result, almost entirely attributable to not examining another specimen. The current definition of sputum smear-positive TB requires two positive smears or one positive smear result plus more complex confirmatory evidence. Accepting a single positive examination as sufficient for the definition would greatly increase the sensitivity of the surveillance definition without sacrificing its specificity.     

综合医院结核病查痰点痰检工作分析

目的分析综合医院门诊可疑肺结核症状者查痰工作情况,探讨综合医院提高涂阳病人发现的措施。方法根据综合医院和结防机构门诊病人登记本、查痰登记本、转诊登记本及结防机构对综合医院的督导和痰检质量控制情况进行综合分析和评价。结果40所综合医院1年间,共登记可疑肺结核症状者11 303例,发现涂阳肺结核859例,涂阳检出率15.6%,转到结防机构的涂阴及未查痰病人2 094例,在结防机构查痰1 685例,发现涂阳肺结核804例,涂阳检出率47.7%,其中未查痰直接转到结防机构查痰1 026例,发现涂阳肺结核551例,涂阳检出率53.7%,痰阴病人转到结防机构再查痰659例,发现涂阳肺结核253例,涂阳检出率38.4%,结防机构门诊查痰25 238例,涂阳检出率55.7%,与综合医院涂阳检出率比较差异有显著性(P<0.05)。结论在综合医院建立查痰点,加大行政干预力度,加强综合医院与结防机构的合作,医院内相关科室建立协调机制,将痰检工作纳入综合医院临床检查常规项目,加强痰检质量控制和结防专业机构对综合医院相关专业人员的培训和复训,是提高传染源发现水平的有效途径。     

Making pragmatic sense of data in the tuberculosis laboratory register

SETTING: Tuberculosis (TB) microscopy network in Moldova, Mongolia, Uganda and Zimbabwe. OBJECTIVE: To evaluate how scrutinising the information recorded in the TB Laboratory Register can assist in improving the performance of the microscopy laboratory network and TB case management. METHODS: Review of records for completeness in registration of age, sex, reason for examination, analysis of variability patterns in serial smears and provision of exemplary statistical process charts of scanty positive results over time in the four countries. RESULTS: A total of 128808 records were analysed. A large proportion of examinees in Uganda (6.9%) and Zimbabwe (3.9%) had no information on sex. The reason for examination was unknown for 7.4%. Among suspects with three smear results with at least one positive result, 56.1% had no variation in the pattern. Statistical process control charts revealed considerable fluctuation in the frequency of scanty positive smears over a calendar year. CONCLUSION: An analysis of information recorded in the TB Laboratory Register not only identifies strengths and weaknesses in the laboratory, it also reveals weaknesses on a much wider scale, in the entire case management system. TB laboratory data can thus demonstrate when, where and what action is indicated, and how performance might be monitored over time.     

Improving sputum microscopy services for the diagnosis of tuberculosis in Peru and Bolivia.

SETTING: Sixteen primary care health centres in Peru and Bolivia. OBJECTIVES: To assess the utilisation of microscopy services in Peru and Bolivia and determine if clinical audit, a quality improvement tool, improves the utilisation of these services. DESIGN: We estimated the percentage of patients with suspected tuberculosis (TB) in whom sputum microscopy was effectively utilised in Peru and Bolivia over two 6-month periods before and after a clinical audit intervention that included standards setting, measuring clinical performance and feedback. RESULTS: Before the intervention, only 31% (95%CI 27-35) of TB suspects were assessed with sputum microscopy in Peru. In Bolivia, 30% (95%CI 25-35) underwent at least two sputum microscopy examinations. After clinical audit, the availability of sputum microscopy results improved by respectively 7% (95%CI 1-12, P < 0.05) and 23% (95%CI 15-30, P < 0.05) over 2 years in Peru and Bolivia. CONCLUSIONS: Despite World Health Organization recommendations that all TB suspects should undergo sputum microscopy before treatment, results are available for further assessment for only one third. This is a potentially serious obstacle to TB case detection. Clinical audit can bring some improvement. We recommend regular monitoring of effective utilisation of microscopy services and investigations to ascertain organisational and structural issues in their uptake and use.     

How many sputum smears are necessary for case finding in pulmonary tuberculosis?

We reviewed the laboratory registers of 42 tuberculosis (TB) diagnostic centres in the southern region of Ethiopia to determine the value of submitting serial sputum samples for the diagnosis of pulmonary TB (PTB) and estimate the proportion of suspects that are smear positive. A total of 15,821 TB suspects submitted three smears each (47,463 smears) in 2000 with a median of 228 per centre. The smear positivity rate (two or more positive smears) was 25%, with a range of 16.8-36.4% per zone. This exceeds the international recommendations of examining 10 suspects to identify one case. A total of 4099 (26%) of the suspects had at least one positive smear with 3753 (91.6%) of the first specimens being positive. A further 303 (7.4%) were negative in the first specimen but had a positive second specimen and 42 (1%) suspects had two negative specimens followed by a positive third smear. The value of the third sputum is negligible as 99% of the cases were identified from the first and second specimens. Reducing the number of specimens to two or even one would have multiple advantages in countries where laboratories are usually over-burdened and are not easily accessible to the population. Submission of two specimens on the same day could improve compliance in submitting samples and collecting results as the number of diagnostic visits would be reduced without significant loss of sensitivity.     

对肺结核可疑者采用症状查痰法提高患者发现率

目的探讨更全面的发现肺结核病例的检查诊断程序。方法在采用通用的胸透筛查法发现肺结核患者的基础上，采用症状查痰法，对有症状且≥3周者，直接做痰结核分枝杆菌检查，并拍摄X线胸片，对按胸透筛查法和症状查痰法发现的患者进行比较；对肺结核诊断程序改进后的结核病患者的发现情况进行分析。结果采用症状查痰法发现活动性肺结核新病例900例，比胸透筛查法多发现活动性肺结核患者73例，患者发现率提高8．8％(73／827)；发现涂阳肺结核病例262例，比胸透筛查法多发现活动性肺结核患者30例，患者发现率提高12．9％(30／232)；培养阳性肺结核病例360例，比胸透筛查法多发现患者63例，患者发现率提高21．2％(63／297)。症状查痰法发现新病例的细菌学检查阳性者的比例高于胸透筛查法，胸透筛查法发现新病例中，涂片阳性者占28．1％(232／827)，痰菌培养阳性者占35．9％(297／827)；而症状查痰法发现新病例中，涂片阳性者占29．1％(262／900)，痰菌培养阳性者占40．0％(360／900)。症状查痰法多检出的活动性肺结核患者73例中，涂阳和菌阳患者的比例均很高，分别为41．1％(30／73)和86．3％(63／73)，较胸透筛查法的检出涂阳比例(28．1％)和菌阳比例(35．9％)高。结论采用症状查痰法比胸透筛查法发现的活动性肺结核患者增加，特别是菌阳肺结核患者的发现率增加21．2％，使这些患者得到及时诊断，有利于结核病传染源的控制。     

Prevalence of pulmonary tuberculosis and comparative evaluation of screening strategies in a Brazilian prison.

SETTING: A prison (1171 male inmates) in Rio de Janeiro, Brazil. OBJECTIVES: To determine the prevalence of active pulmonary tuberculosis (TB) and to assess the performance of several screening strategies. DESIGN: In a cross-sectional study, all inmates underwent chest radiographic screening. Subjects with abnormal findings underwent sputum smear examination and sputum culture. Taking this strategy as the reference, we assessed three targeted screening strategies to identify TB suspects: Strategy 1: cough >3 weeks; Strategy 2: WHO score > or = 5; Strategy 3: presence of at least one potentially TB-related symptom. RESULTS: The prevalence of TB cases was 4.6% (48/1052) and 2.7% for definite TB cases. If TB suspects identified by targeted screening had sputum smear examination alone, 37 (86.0%) of the 43 cases would have been missed by Strategy 1, 34/43 (79.1%) by Strategy 2 and 34/43 (79.1%) by Strategy 3. If TB suspects had both sputum smear examination and, for smear-negative subjects, chest radiography, respectively 28/43 (65.1%), 18/43 (41.9%) and 13/43 (30.2%) of cases would have been missed. CONCLUSION: All three targeted screening strategies were unreliable. Given the importance of early TB diagnosis in overcrowded and highly endemic settings, routine radiography-based screening may be warranted.     

Cost-effectiveness of novel diagnostic tools for the diagnosis of tuberculosis

SETTING: The potential cost-effectiveness of improved diagnostic tests for tuberculosis (TB) in resource-limited settings is unknown. OBJECTIVE: To estimate the incremental cost-effectiveness of a hypothetical new point-of-care TB diagnostic test in South Africa, Brazil and Kenya. DESIGN: Decision-analysis model, adding four diagnostic interventions (sputum smear microscopy, new test, smear plus new test and smear plus TB culture) to a baseline of existing infrastructure without smear. RESULTS: Adding sputum smear was estimated to be more cost-effective (incremental cost per disability-adjusted life year [DALY] of $86 [South Africa], $131 [Brazil], $38 (Kenya]) than a new TB diagnostic with 70% sensitivity, 95% specificity and price of $20 per test ($198 [South Africa], $275 [Brazil], $84 [Kenya]). However, compared to sputum smear, smear plus new test averted 46-49% more DALYs per 1000 TB suspects (321 vs. 215 [South Africa], 243 vs. 166 [Brazil], 790 vs. 531 [Kenya]), at an incremental cost of $170 (Kenya) to $625 (Brazil) per DALY averted. Cost-effectiveness was most sensitive to the specificity and price of the new test, the baseline TB case detection rate and the discount rate. CONCLUSION: Novel diagnostic tests for TB are potentially highly cost-effective. Cost-effectiveness is maximized by high-specificity, low-cost tests deployed to regions with poor infrastructure.     

Diagnostic yield of repeated smear microscopy examinations among patients suspected of pulmonary TB in Shandong province of China.

OBJECTIVES: To analyse the yield of five repeated smear microscopy examinations for the diagnosis of smear-positive pulmonary tuberculosis (TB). METHODS: Patients with respiratory symptoms and abnormal chest X-rays provided five spontaneous sputum samples for acid-fast bacilli (AFB) smear microscopy in one of nine county laboratories. RESULTS: Of 9302 patients with respiratory symptoms and abnormal X-rays, 6437 (69%) had at least one smear-positive sputum. Of these, 84.5% were diagnosed on the first smear, 96.7% on the first two smears, and 99.9% on the first three sputum smears. The fourth and fifth sputum smears yielded only seven additional cases (0.1%). CONCLUSIONS: Smear microscopy examination of two spontaneous sputum specimens is the most efficient, and three sputum smear examinations provide a diagnosis in almost all cases.     

Is it valuable to examine more than one sputum smear per patient for the diagnosis of pulmonary tuberculosis?

The simplest, cheapest, and fastest diagnostic method for tuberculosis (TB) is the detection of acid-fast bacilli (AFB) by microscopy. The algorithm advised for the diagnosis of TB recommends examination of three consecutive sputum specimens from TB suspects for the presence of AFB. In the present study, we evaluated the contribution of each specimen to the final detection of TB suspect patients with culture-proven disease. The collection and analysis of retrospective data on patients with culture-proven pulmonary TB, from June 2002 to August 2006 at Dokuz Eylul University Hospital, Turkey, have enabled us to assess the value of examining two sputum specimens in diagnosing this disease. AFB were detected from one or more sputum specimens with direct microscopy in 42% of the cases. An analysis of results of smear examination showed that 97% of AFB were detected from the first specimen and only 3% were obtained from the second smear. The third specimen did not have any additional diagnostic value for the detection of AFB by microscopy. As a conclusion the present study shows that examining two sputum smears is sufficient for the early detection of AFB in our laboratory.     

福清市设立乡镇初筛点提高结核病人发现探讨

目的　探讨在乡镇卫生院设立初筛点提高结核病发现率。方法 将全市22个乡镇(农场)分成6个初筛点,由其中1个中心卫生院负责痰涂片、X线检查,经市(县)结防科定诊。结果 2003年6个初筛点可疑症状者就诊率1.93%,查痰率85.8%,涂阳病人占67.2%,涂阳新登记率40.6/10万,分别比2002年提高了91.1%,14.4%,60.4%,20.1%。结论 通过乡镇初筛既可提高结核病服务的可行性,又能提高涂阳病例发现。     

Health-seeking behaviour among adults with prolonged cough in Vietnam

Objective To assess health‐seeking behaviour among adults with prolonged cough in a population‐based, nationally representative sample in Vietnam. Methods Cross‐sectional survey conducted from September 2006 to July 2007. All inhabitants aged ≥15 years were invited for screening for cough, history of tuberculosis (TB) treatment and chest X‐ray (CXR) examination. TB suspects, defined as any survey participant with CXR abnormalities consistent with TB, or productive cough for more than 2 weeks or TB treatment either currently or in the preceding 2 years submitted sputum specimens for smear examination and culture and provided information on health‐seeking behaviour in an in‐depth interview. Results Of 94 179 persons participating in the survey, 4.6% had prolonged productive cough. Forty‐four percentage of those had sought health care and reported pharmacies (35%), commune health posts (29%), public hospitals (24%) and private physicians (10%) as first point of contact. Only 7% had undergone sputum smear examination. Of TB suspects with prolonged productive cough, 2.9% were diagnosed with TB; 10.2% of these reported smear and 21.9% reported X‐ray examination when visiting a health care facility. The average patient delay was 4.1 weeks (95% CI: 3.9–4.4) among cough suspects and 4.0 weeks (95% CI: 3.1–4.9) among TB cases. Conclusions In this Vietnamese survey, nearly half of persons with cough for more than 2 weeks had visited a health care provider. The commonest first health facility contacted was the pharmacy. Sputum smears were rarely examined, except in the provincial TB hospital. Our findings highlight the need to improve diagnostic practices by retraining health staff on the performance of sputum examination for TB suspects.     

Prevalence of smear-positive pulmonary tuberculosis in a rural district of Ethiopia.

SETTING: A rural district in Southern Ethiopia. OBJECTIVE: To estimate the prevalence of smear-positive pulmonary tuberculosis (TB). DESIGN: In this cross-sectional study, adults aged >14 years were surveyed by home-to-home visit, and asked about cough of > or = 2 weeks with or without sputum, chest pain or difficulty in breathing. Symptomatic suspects submitted three sputum samples for standard smear microscopy. RESULTS: Of 16697 adults surveyed, 436 (2.6%) were symptomatic and submitted sputum samples. Thirteen (3%) were positive for acid-fast bacilli, and the prevalence of smear-positive TB was 78 per 100 000 population (95%CI 36-120). Twenty-four smear-positive cases identified through the existing health care delivery were on anti-tuberculosis medication at the time of the survey. The ratio of smear-positive cases on treatment to those newly detected by the survey was 2:1. CONCLUSION: The prevalence of TB in this rural setting was unexpectedly low. For every two cases of smear-positive TB on treatment, there was one undetected infectious case in the community. However, as our screening technique did not allow detection of cases who did not report symptoms, the true prevalence may have been underestimated.     

Diagnostic value of repeated sputum examinations in pulmonary tuberculosis: how many sputum specimens are adequate?

The aim of this study was to assess the value of examining multiple sputum specimens in the diagnosis of pulmonary tuberculosis (PTB). We analyzed sputum smear and culture results of patients diagnosed with culture-proven PTB during 2002. In 1027 patients, the diagnosis was established by detection of Mycobacterium tuberculosis bacilli in sputum samples. The number of sputum specimens submitted to laboratory was one in 634 cases, two in 167 cases, three in 186 cases and more than three in 48 cases. 760 (74%) cases had positive smear examination result. The first sputum smear examination was positive in 82.3% of smear positive cases. Either the first or the second sputum was diagnostic in 94.9% of these cases. Smear examination of third sputum revealed 4.2% additional diagnostic yield. In 863 (84%) cases, culture examination of the first sputum was positive. The second and the third sputum culture examinations revealed additional diagnostic yield of 11% and 4.5%, respectively. Percent 95 of culture-proven cases were diagnosed with the first two sputum cultures. In conclusion the majority of PTB cases can be diagnosed with the examination of two sputum specimens. Three or more sputum specimens submitted obtain a small additional diagnostic yield.     

Optimal tuberculosis case detection by direct sputum smear microscopy: how much better is more?

SETTING: A tuberculosis control project in Bangladesh. OBJECTIVE: To define the efficiency of numbers of microscopic fields screened and the sputum collection scheme used for diagnostic smear examination. DESIGN: Quality controllers noted cumulative numbers of acid-fast bacilli per 100 fields screened. The incremental diagnostic yield of different sputum sampling strategies was determined. Doubtful series were re-checked and/or further samples examined. RESULTS: Acid-fast bacilli were found in 99.6% of 1412 positive and in 79.3% of 576 scanty slides in the first 100 fields. Examination of a third specimen yielded a maximum of 2.7% positives incrementally. The most efficient strategy, using three morning specimens, yielded 94.2% positives on the first and 1.0% on the third sputum; although 10% of suspects did not return, only 1.5% of the positives were among them and more cases were confirmed and treated. The positive predictive value of a single positive or scanty smear was very high (99.2%). CONCLUSIONS: Reading more than 100 fields per smear or examining a third sputum has insufficient marginal returns to justify the workload. Examining morning samples only is more efficient, and their collection does not necessarily inconvenience patients. Treatment can be started on the basis of one positive smear. Provided that a well functioning system of smear-microscopy quality control is in place, we propose a strategy based on examination of two morning sputum samples for negative suspects, with the diagnosis based on a single positive result.     

Screening tuberculosis suspects using two sputum smears.

SETTING: Ntcheu district hospital, Malawi. OBJECTIVE: To assess a screening strategy for tuberculosis (TB) suspects using two sputum smears. DESIGN: A strategy of screening all TB suspects with two sputum smears for 6 months (1 July-31 December 1998) was compared with the period 1 January to 30 June 1998 during which the strategy of screening TB suspects with three sputum smears was in use. All chest radiographs of patients with negative sputum smears were assessed, and in those with pulmonary cavities and extensive disease a third sputum smear was examined. Data were collected from the laboratory sputum register and the TB register. The two 6-month periods were compared. RESULTS: In the laboratory register, using a two-sputum strategy, 186 (16%) of 1152 TB suspects were smear-positive, a result that was no different than when the three-sputum strategy was used, where 173 (16%) of 1106 TB suspects were smear-positive. The clinical pattern of TB using the different screening strategies was similar, with 58% of registered patients smear-positive with the two-sputum strategy and 54% smear-positive with the three-sputum strategy. In the first 6 months 3177 sputum smears were examined compared to 2266 smears in the second 6 months, a 29% reduction in the number of smears examined. The cost of consumables using the strategy of three sputum smears was USD $731 compared with USD $521 using the strategy of two sputum smears. C O N C L U S I O N S: Screening TB suspects using two sputum smears is as effective as screening using three sputum smears, and is associated with less laboratory work and savings in costs.