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.     

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.     

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 a third serial sputum smear examination in the diagnosis of tuberculosis in Moldova and Uganda.

SETTING: Twenty-four and 30 tuberculosis (TB) microscopy laboratories in Moldova and Uganda, respectively. OBJECTIVE: To estimate the workload required to identify one additional case of TB with a third serial sputum smear examination. METHODS: Retrospective laboratory register study to determine the prevalence and the incremental yield of TB cases from a third serial sputum smear examination among suspects in Moldova and Uganda, with the reciprocal of the product of these two fractions providing the number of examinations required to identify one additional TB case. RESULTS: In Moldova, 9% (1141/12525) and in Uganda 20% (7280/36054) of suspects met the TB case definition with at least one positive sputum smear. The incremental yield from the third examination was 4% in Moldova and 3% in Uganda. To detect one additional TB case on a third smear, 273 examinations (95%CI 200-389) in Moldova and 175 (95%CI 153-222) in Uganda were thus required. This corresponded to an average of 11 days (8-16) and 7 days (6-9), respectively, to diagnose one additional case of TB. CONCLUSION: In both countries, the third serial sputum smear examination was inefficient in diagnosing sputum smear-positive TB.     

A comprehensive comparison of Ziehl-Neelsen and fluorescence microscopy for the diagnosis of tuberculosis in a resource-poor urban setting.

SETTING: Nairobi City Council Chest Clinic, Kenya. OBJECTIVES: To establish the efficiency, costs and cost-effectiveness of six diagnostic strategies using Ziehl-Neelsen (ZN) and fluorescence microscopy (FM). DESIGN: A cross-sectional study of 1398 TB suspects attending a specialised chest clinic in Nairobi subjected to three sputum examinations by ZN and FM. Lowenstein-Jensen culture was used as the gold standard. Cost analysis included health service and patient costs. RESULTS: Of 1398 suspects enrolled, 993 (71%) had a complete diagnostic work-up involving three sputum specimens for ZN and FM, culture and chest X-ray (CXR). Irrespective of whether ZN or FM was used on one, two or three smears, the overall diagnostic process detected 92% culture-positive cases. Different strategies affected the ratio of smear-positive to smear-negative TB; however, FM was more sensitive than ZN (P < 0.001). FM performance was not affected by the patient's HIV status. The cost per correctly diagnosed smear-positive case, including savings, was 40.30 US dollars for FM on two specimens compared to 57.70 US dollars for ZN on three specimens. CONCLUSION: The FM method used on one or two specimens is more cost-effective and shortens the diagnostic process. Consequently, more patients can be put on a regimen for smear-positive TB, contributing to improved treatment and reducing transmission.     

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.     

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。     

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.     

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.     

Informing the TB suspect for sputum sample collection and communicating laboratory results in Nicaragua: a neglected process in tuberculosis case finding

OBJECTIVE: To assess the patient information process before sputum sample collection, the quality of sputum sample and transmission of acid-fast bacilli (AFB) examination results to TB suspects, in three local areas of Nicaragua. METHODS: (a) directed interviews of consecutive series of TB suspects whose sputum had been examined for AFB; (b) directed interview of health personnel; and (c) assessment of the sputum sample quality. RESULTS: A total of 115 TB suspects and 33 health personnel were interviewed and 625 sputum samples were assessed. Results show multiple weaknesses in the process of information to the patient during sputum collections, as well as in the communication of results. CONCLUSIONS: This study unveiled an aspect usually overlooked of case finding, that is, the information process during sputum production, sputum sample quality, and the communication of results to the TB suspects. The results illustrate the need for routine assessment of the whole diagnostic process.     

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.     

Comparison of scanty AFB smears against culture in an area with high HIV prevalence.

To verify among tuberculosis (TB) suspects attending hospitals in Abuja, Nigeria, if sputum smears graded as scanty are false-positive, sputum smears from 1068 patients were graded with the International Union Against Tuberculosis and Lung Disease classification. One specimen was cultured. Eight hundred and twenty-four (26%) smears were positive, 137 (4%) scanty and 2243 negative. Of 1068 cultures, 680 (64%) were positive. One hundred and thirty (95%) scanty and 809 (98%) positive smears were culture-positive. Twelve of 18 patients with a single scanty smear and 51 of 52 with > or = 2 scanty smears were culture-positive. Fewer than < 5% scanty results, < 1% of the patients treated for TB, are false-positive.     

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.     

Reducing the number of sputum samples examined and thresholds for positivity: an opportunity to optimise smear microscopy.

SETTING: Urban health clinic, Nairobi. OBJECTIVE: To evaluate the impact on tuberculosis (TB) case detection and laboratory workload of reducing the number of sputum smears examined and thresholds for diagnosing positive smears and positive cases. DESIGN: In this prospective study, three Ziehl-Neelsen stained sputum smears from consecutive pulmonary TB suspects were examined blind. The standard approach (A), > or = 2 positive smears out of 3, using a cut-off of 10 acid-fast bacilli (AFB)/100 high-power fields (HPF), was compared with approaches B, > or = 2 positive smears (> or = 4 AFB/100 HPF) out of 3, one of which is > or = 10 AFB/100 HPF; C, > or = 2 positive smears (> or = 4 AFB/100 HPF) out of 3; D, > or = 1 positive smear (> or = 10 AFB/100 HPF) out of 2; and E, > or = 1 positive smear (> or = 4 AFB/100 HPF) out of 2. The microscopy gold standard was detection of at least one positive smear (> or = 4 AFB/100 HPF) out of 3. RESULTS: Among 644 TB suspects, the alternative approaches detected from 114 (17.7%) (approach B) to 123 cases (19.1%) (approach E) compared to 105 cases (16.3%) for approach A (P < 0.005). Sensitivity ranged between 82.0% (105/128) for A and 96.1% (123/128) for E. The single positive smear approaches reduced the number of smears by 36% compared to approach A. CONCLUSION: Reducing the number of specimens and the positivity threshold to define a positive case increased the sensitivity of microscopy and reduced laboratory workload.     

The effect of decentralisation on tuberculosis services in three states of Sudan.

SETTING: Referral hospitals and primary health care (PHC) facilities in Khartoum, Red Sea and Gadaref States. OBJECTIVES: To measure the effect of the decentralisation of the tuberculosis (TB) services on the clinical profile and treatment outcome of tuberculosis. DESIGN: A cohort study of case detection and treatment outcome using information routinely collected comparing patients attending PHC facilities and referral hospitals in selected locations in Sudan. RESULTS: Two-thirds of all TB patients were diagnosed in referral hospitals and one-third in PHC facilities. In PHC facilities, women represented 46% of notified cases, compared to 37.9% in referral hospitals (OR 1.398, 95%CI 1.343-1.455). Older age groups were more likely to prefer PHC facilities to referral hospitals. In referral hospitals, 38% were cured, 29.3% completed treatment without smear examination and 17.3% defaulted, while in PHC facilities 58% were cured, 17.8% completed treatment without smear examination and 11.6% defaulted. CONCLUSION: PHC facilities provide care for a higher proportion of women and older age groups of tuberculosis patients, suggesting a higher level of accessibility for these groups. A higher cure rate and a lower default rate were noted in PHC facilities, possibly reflecting better conditions for directly observed treatment and follow-up.     

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.     

Prevalence of tuberculosis suspects and their healthcare-seeking behavior in urban and rural Jordan

To determine the prevalence and healthcare-seeking behavior of tuberculosis (TB) suspects in Middle and South Jordan. A community-based survey was carried out between June-September 2005, whereby 61,730 adult household members were inquired about the presence of persistent cough for more than three weeks to identify TB suspects. These adults were then interviewed and referred to the nearest health center for clinical and sputum smear examination. Of the 61,730 surveyed household members, 1,544 (2.51%) were identified as TB suspects, of these two were sputum smear positive pulmonary TB. The first action with the onset of symptoms was to visit the health centers. Reasons for timely seeking care were accessibility of the facilities and confidence in obtaining a cure, and obstacles were belief that symptoms would resolve and economic constraints in rural residents. Females, rural residents, expatriates, and using private means of transportation were predictors of delay in seeking care for more than three weeks. This study has set the baseline information about the prevalence of TB suspects in Jordan and their healthcare-seeking behavior that shows community preference to seek care at health centers. These should be upgraded and the health workers trained on suspect management to enhance the TB elimination efforts.     

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.     

Gender differences in relation to sputum submission and smear-positive pulmonary tuberculosis in Malawi.

OBJECTIVE: To examine gender differences in sputum submission and sputum smear positivity. METHODS: Laboratory registers in all diagnostic units in eight districts in Malawi were examined for the years 1995 and 1996. RESULTS: During a 12-month period (averaged between 1995 and 1996), 26,624 new TB suspects submitted sputum samples, 3282 of which (12.3%) were smear-positive. Significantly more males submitted sputum (52%) compared with females (48%), and significantly more males (53%) were smear-positive compared with females (47%, P < 0.05). Rates of sputum submission per 100,000 adults were also significantly higher for males (1203) than females (1032). CONCLUSION: In Malawi, fewer females are submitting sputum samples and are being diagnosed with smear-positive TB compared with males.