Pre-treatment delay and out of pocket expenses by notified new tuberculosis patients in an Indian mega city

BACKGROUND

Study was carried out to find out delay from onset of symptoms and out of pocket expenditure (OOPE) until initiation of anti-TB treatment (ATT) by new Tuberculosis (TB) patients registered in public health facilities in Bengaluru.

METHODS

Notified patients (N = 228) selected purposively were interviewed at initiation of ATT regarding number and type of facilities visited and delay in initiating ATT. OOPE was elicited separately for in- and out-patient visits, towards consultation, purchase of medicines, diagnostic tests, transportation, hospitalization and food. Dissaving or money borrowed was ascertained.

RESULTS

Two-thirds of participants were 15-44 years of age and 56% were males, mean annual household income was $4357. About 75% first visited a private health facility; 68% and 87% respectively were diagnosed and started on ATT in public sector after visiting an average of three facilities and after a mean delay of 68 days; the median delay was 44 days. Of mean OOPE of $402, 54% was direct medical expenditure, 5% non-medical direct and 41% indirect. OOPE was higher for Extra-pulmonary TB compared to PTB and when number of health facilities visited before initiating treatment was >3 compared to those who visited ≤3 and when the time interval between onset of symptoms and treatment initiation (total delay) was >28 days compared to when this interval was ≤28 days. About 20% suffered catastrophic expenditure; 34% borrowed money and 37% sold assets.

CONCLUSION

Concerted efforts are needed to reduce delay and OOPE in pre-treatment period and social protection to account for indirect expenditure.

Active tuberculosis case finding in India - The way forward

Community based active case finding (ACF) for tuberculosis (TB) has seen resurrection in the current armamentarium of many TB managers in their fight toward eliminating TB. This article explores the accuracy and approximate cost of various ACF algorithms currently in vogue in India or those which could be useful, while inputting the sensitivity and specificity of screening and diagnostic tools as estimated from recently conducted community based surveys. This analysis informs that ACF may be prioritized to higher prevalence settings and the diagnostic algorithm for specific setting may be chosen taking into account the expected prevalence, estimated accuracy of the algorithm and resource availability. Further, chest X-ray cannot be used alone as a diagnostic tool and can be relied upon for this purpose when at least one of the three sputum specimen is smear positive. Accuracy of Xpert MTB/RIF as a diagnostic tool in community situations needs to be investigated further. The review brings out significant proportions of initial default and default during treatment among cases detected through ACF thus emphasizing the need for heightened efforts toward preventing the same. The article rounds off emphasizing priority to addressing barriers to speedy scale up of more sensitive diagnostic tools for health center based case finding including in private sector and ACF in high risk clinical groups for early and efficient case detection. It concludes by putting forth certain research areas that would strengthen future efforts.

Sensitivity and specificity of screening tools and smear microscopy in active tuberculosis case finding

SETTING

Community based five pulmonary tuberculosis (PTB) surveys among adults.

OBJECTIVES

Estimate sensitivity and specificity of screening tools for PTB and sputum microscopy.

METHODS

For each survey site, we estimated sensitivity and specificity of different screening criteria and microscopy against culture; pooled estimates were obtained using Random Effects Model.

RESULTS

Sensitivity of cough alone, screening for any symptom (persistent cough ≥2 weeks, fever or chest pain ≥1 month, hemoptysis), any symptom or history of anti-TB treatment (h/o ATT) were 56.2%, 66% and 71.2% respectively; specificities were 95.3%, 93.8% and 92.7% respectively. X-ray when used alone for primary screening had sensitivity and specificity of 76.6% and 97.3% respectively. When used along with screening for cough, these figures were 94.3% and 93.1%, and 100% and 97.3% when used with any symptom and h/o ATT. When used for secondary screening, sensitivity and specificity of X-ray was 66.8% and 87.8% respectively after primary screening for cough, 65.0% and 89.8% after screening for any symptom, and 67.1% and 86.7% when used after screening for any symptom or h/o ATT. Pooled sensitivity and specificity of smear was 46.2% and 99.3% respectively.

CONCLUSION

Program managers may use these estimates while evaluating algorithms for active case finding.

Estimating tuberculosis incidence from primary survey data: a mathematical modeling approach

BACKGROUND:

There is an urgent need for improved estimations of the burden of tuberculosis (TB).

OBJECTIVE:

To develop a new quantitative method based on mathematical modelling, and to demonstrate its application to TB in India.

DESIGN:

We developed a simple model of TB transmission dynamics to estimate the annual incidence of TB disease from the annual risk of tuberculous infection and prevalence of smear-positive TB. We first compared model estimates for annual infections per smear-positive TB case using previous empirical estimates from China, Korea and the Philippines. We then applied the model to estimate TB incidence in India, stratified by urban and rural settings.

RESULTS:

Study model estimates show agreement with previous empirical estimates. Applied to India, the model suggests an annual incidence of smear-positive TB of 89.8 per 100 000 population (95%CI 56.8–156.3). Results show differences in urban and rural TB: while an urban TB case infects more individuals per year, a rural TB case remains infectious for appreciably longer, suggesting the need for interventions tailored to these different settings.

CONCLUSIONS:

Simple models of TB transmission, in conjunction with necessary data, can offer approaches to burden estimation that complement those currently being used.

Integration and decentralisation of TB-HIV services increases HIV testing of TB cases in Rajasthan, India

The proportion of tuberculosis (TB) patients tested for the human immunodeficiency virus (HIV) in the state of Ra-jasthan, India, is limited by the availability of HIV testing facilities. Rajasthan implemented a policy of initiating TB-HIV diagnosis at all health institutions in July 2013. The number of TB diagnostic facilities increased from 33 to 63 in Banswara District and from 22 to 68 in Jhunjhunu District, while the number of HIV testing facilities in these districts increased from 1 to 53 and from 10 to 81, respectively, after the policy implementation. The proportion of TB patients tested for HIV increased by respectively 27% and 19%.

Cost analysis of different diagnostic algorithms for pulmonary tuberculosis varying in placement of Xpert MTB/RIF

BACKGROUND

We undertook cost analysis for diagnosis of pulmonary tuberculosis (PTB) using present algorithm under Revised National Tuberculosis Control programme and using Xpert MTB/RIF (Xpert) as frontline test or in conjunction with smear microscopy and/or chest radiography.

METHODS

Costs were estimated for different strategies: (A) present algorithm involving sputum smear examination followed by antibiotic trial in smear negative patients, repeat smear examination (RE) if symptoms continue and chest radiography if RE negative; (B) direct Xpert; (C) smear microscopy followed by Xpert in smear negative patients; (D) radiography followed by Xpert in those having abnormal pulmonary shadows; and (E) smear examination followed by radiography among smear negative patients and Xpert in presence of abnormal pulmonary shadow.

RESULTS

Cost to program was estimated lowest with Strategy A and highest with Strategy B. Compared to the latter, program cost reduces by 7%, 4.5%, and 17.4% by strategies C, D, and E, respectively. Cost to the group of individuals with presumptive PTB and their attendants is significantly higher for Strategy A compared to other four strategies. Among the latter, the patients' cost was minimum with Strategy B and maximum with Strategy C. Program cost per case diagnosed was lowest by Strategy A and highest by Strategy B. Patient cost per case diagnosed was highest by Strategy A and lowest by Strategy B. Using Xpert, Strategy E had the lowest program as well as overall cost per case diagnosed.

CONCLUSION

Strategy E may be chosen for diagnosis of PTB. When resources would no longer be a constraint, direct Xpert would reduce costs incurred by the patients.

Impact of awareness drives and community-based active tuberculosis case finding in Odisha, India

India's Revised National Tuberculosis Control programme employs passive case detection. The new sputum smear-positive case detection rate is less than 70% in Odisha State. During April-June 2012, active case finding (ACF) was conducted through awareness drives and field-based tuberculosis (TB) screening in select communities with the lowest case detection rates. During the campaign, 240 sputum smear-positive TB cases were detected. The number of smear-positive cases detected increased by 11% relative to April-June 2011 in intervention communities compared to an 0.8% increase in non-intervention communities. ACF brought TB services closer to the community and increased TB case detection.

Tuberculosis case notification by private practitioners in Pune, India: how well are we doing?

SETTING

Pimpri Chinchwad Municipal Corporation area, Pune, India.

OBJECTIVE

To assess the proportion of private practitioners (PPs) who notified tuberculosis (TB) patients during February-April 2013 and their contribution to the overall number notified, and to determine their perceived challenges in reporting TB cases.

DESIGN

Mixed-method study including an analysis of notification data, followed by in-depth interviews with PPs. Interviews were transcribed and inductive content analysis was performed to derive themes.

RESULTS

Of 831 PPs, 533 (64%) participated in case notification; of these 87 (16%) notified at least one TB case during the study period. In all, 138 TB cases were notified by PPs, accounting for 20% of the total TB cases notified. Emerging themes among perceived challenges and barriers were lack of complete knowledge about TB notification, fear of a breach of patient confidentiality, lack of a simplified operational mechanism of notification, and lack of trust and coordination with the government health system.

CONCLUSION

About two thirds of PPs participated in case notification and contributed significantly to the overall TB cases notified. India's national TB programme should focus on training PPs and targeted media communication campaigns, and establish alternative mechanisms for notification, such as the internet and mobile telephones, to overcome perceived barriers.

Are registered sputum smear-negative tuberculosis patients in Karnataka, India, diagnosed by national algorithm?

SETTING

Four districts of Karnataka State, India, that have implemented the National Tuberculosis Control Programme (RNTCP).

OBJECTIVE

To assess the proportion of patients diagnosed according to the nationally recommended algorithm among new smear-negative (NSN) PTB cases registered under the RNTCP.

METHODS

Information on 201 registered NSN-PTB patients as regards date of initial sputum examination, repeat sputum examination and chest X-ray (CXR) if undertaken, treatment initiation and number of days of antibiotic treatment after initial sputum examination, were collected through record review and patient interviews. In patients with negative or unknown human immunodeficiency virus (HIV) status, the algorithm was considered completed if the patient underwent initial sputum examination, antibiotic trial for ⩾10 days, repeat sputum examination ⩾10 days after initial sputum examination, CXR after repeat sputum examination and anti-tuberculosis treatment ⩾10 days after initial sputum examination. In HIV-positive patients, the algorithm was considered completed if CXR was performed after or at the same time as initial sputum examination.

RESULTS

Complete information was available for 170 patients. Of these, the algorithm was completed in 14 (8.2%, 95%CI 0.9-15.5): 1/140 patients with negative or unknown HIV status and 13/30 HIV-positive patients.

CONCLUSION

The algorithm was not completed in most patients registered for treatment. Measures are needed to improve the diagnostic process for smear-negative PTB.

A descriptive study of tuberculosis case finding in private health care facilities in a South Indian district

SETTING

A South Indian district providing anti-tuberculosis services through the Revised National TB Control Programme (RNTCP) and private health care facilities.

OBJECTIVE

To ascertain the profile of tuberculosis (TB) patients diagnosed and/or treated in private health care facilities.

METHODS

Data on TB cases diagnosed and/or treated in all clinical departments of the medical college, 83 nursing homes and RNTCP health care facilities were collected prospectively.

RESULTS

About 83% of new TB cases recorded in the private medical college, 47% in nursing homes and 24.5% in RNTCP TB registers were extra-pulmonary. The proportion of retreatment cases was respectively 5.5%, 9.6% and 19.8%. The proportion of males and those in the economically productive age group were similar in the three data sources. About 94% of cases diagnosed in the medical college and 55% in nursing homes were registered for treatment under the RNTCP. About 11% of the smear-positive patients diagnosed in RNTCP were initial defaulters.

CONCLUSION

The proportion of extra-pulmonary cases was higher in the medical college and nursing homes and that of retreatment cases was lower than in the RNTCP.

Implementation efficiency of a diagnostic algorithm in sputum smear-negative presumptive tuberculosis patients

BACKGROUND

For the diagnosis of smear-negative pulmonary tuberculosis (PTB), India's Revised National Tuberculosis Control Programme (RNTCP) recommends a course of broad-spectrum antibiotics after negative smear on initial sputum examination, followed by repeat sputum examination and chest X-ray (CXR).

OBJECTIVES

1) To ascertain the proportion of presumptive PTB patients smear-negative on initial sputum examination who completed the diagnostic algorithm, and 2) to investigate barriers to the completion of the algorithm.

METHODS

In Karnataka State, India, 256 study participants were interviewed in 2012 to ascertain the number of days antibiotics had been prescribed and consumed, the number of re-visits to health centre(s), whether repeat sputum examinations had been performed, whether or not CXR had been performed and when, and whether PTB had been diagnosed. In-depth interviews were conducted with 19 medical officers.

RESULTS

The diagnostic algorithm was completed in 13 (5.1%) of 256 participants; three were diagnosed with PTB without completing the algorithm. Most medical officers were unaware of the algorithm, had trained 5-10 years previously, prescribed antibiotics for <10 days and advised CXR without repeat sputum examination, irrespective of the number of days of antibiotic treatment. Other main reasons for non-completion of algorithm were patients not returning to the health centres and a proportion switching to the private sector.

CONCLUSION

Refresher training courses, raising patient awareness and active follow-up of patients to complete the algorithm are suggested.

Role of pre-Xpert® screening using chest X-ray in early diagnosis of smear-negative pulmonary tuberculosis

In a sub-district level hospital in South India, the proportion of patients with abnormal chest X-ray (CXR) was evaluated among smear-negative, Xpert® MTB/RIF (Xpert) positive individuals with pulmonary tuberculosis (PTB) symptoms; 384 smear-negative PTB individuals with PTB symptoms and without a history of anti-tuberculosis treatment underwent CXR and Xpert testing of one sputum specimen. Of 378 individuals with both Xpert and CXR results available, 14 were positive for Mycobacterium tuberculosis. Of these, 13 (92.9%) had an abnormal CXR and one was normal. This study highlights the usefulness of CXR before Xpert testing, which needs further validation.

Treatment outcome of tuberculosis patients in a clinic of Bangalore

A total of 112 cases (New = 101, previously treated = 11) were diagnosed as suffering from tuberculosis (TB) at a private clinic in Bangalore city. The clinic identified TB suspects, established diagnosis of TB, administered direct observation of treatment (DOT), maintained treatment cards and undertook defaulter retrieval actions as and when required. The Revised National Tuberculosis Control Programme (RNTCP) provided support in terms of sputum microscopy supply of patient-wise drug boxes and registration of patients. Ninety six (95.1%) of new cases and 10 (90.9%) of previously treated cases had successful treatment outcome. Most patients completed treatment within the prescribed period. No TB deaths were reported during the period of treatment.

Annual risk of tuberculous infection among schoolchildren in Bhutan

SETTING

School-based survey in the mountainous nation of Bhutan.

OBJECTIVE

To estimate the annual risk of tuberculous infection (ARTI) among children aged 6-8 years.

DESIGN

A national-level tuberculin survey was carried out among children attending 64 schools selected by two-stage cluster sampling. The study population was comprised of children without and with bacille Calmette-Guérin (BCG) scar. Tuberculin testing was performed using 2 tuberculin units of purified protein derivative RT23. The maximum transverse diameter of induration was measured at 48-72 h.

RESULTS

Of 6087 satisfactorily test-read children, 82% had a BCG scar. The frequency distribution of tuberculin reaction sizes in all children (with and without BCG scar) did not reveal the mode for tuberculous reactions. The mode seen at 17 mm among children without BCG scar was applied to estimate the prevalence of infection among all children using the mirror-image method. Estimation was also undertaken by shifting the mode by 1 mm on either side. The ARTI computed from the prevalence thus estimated varied between 0.2% and 0.7%. There was no difference in the prevalence of infection by BCG scar status, implying that the estimated ARTI was not influenced by BCG-induced tuberculin sensitivity.

CONCLUSION

The ARTI has declined in Bhutan compared to the 1991 survey estimate of 1.9%.

Trends in the annual risk of tuberculous infection in India

SETTING

Twenty-four districts in India.

OBJECTIVES

To evaluate trends in annual risk of tuberculous infection (ARTI) in each of four geographically defined zones in the country.

STUDY DESIGN

Two rounds of house-based tuberculin surveys were conducted 8-9 years apart among children aged 1-9 years in statistically selected clusters during 2000-2003 and 2009-2010 (Surveys I and II). Altogether, 184,992 children were tested with 1 tuberculin unit (TU) of purified protein derivative (PPD) RT23 with Tween 80 in Survey I and 69,496 children with 2TU dose of PPD in Survey II. The maximum transverse diameter of induration was measured about 72 h after test administration. ARTI was computed from the prevalence of infection estimated using the mirror-image method.

RESULTS

Estimated ARTI rates in different zones varied between 1.1% and 1.9% in Survey I and 0.6% and 1.2% in Survey II. The ARTI declined by respectively 6.1% and 11.7% per year in the north and west zones; no decline was observed in the south and east zones. National level estimates were respectively 1.5% and 1.0%, with a decline of 4.5% per year in the intervening period.

CONCLUSION

Although a decline in ARTI was observed in two of the four zones and at national level, the current ARTI of about 1% in three zones suggests that further intensification of TB control activities is required.

High risk of tuberculous infection in North Sulawesi Province of Indonesia

SETTING

Of all the provinces in Indonesia, the highest tuberculosis (TB) case notification rates are reported from North Sulawesi Province.

OBJECTIVE

To estimate the annual risk of tuberculous infection (ARTI) among schoolchildren in the 6-9 year age group.

METHODS

A cross-sectional survey was carried out in 99 schools selected by a two-stage sampling process. Children attending grades 1-4 in the selected schools were administered intradermally with 2 tuberculin units (TUs) of purified protein derivative RT23 with Tween 80, and the maximum transverse diameter of induration was measured about 72 h later. A total of 6557 children in the 6-9 year age group were satisfactorily test-read, irrespective of their bacille Calmette-Guérin (BCG) vaccination status.

RESULTS

Based on the frequency distribution of reaction sizes obtained among satisfactorily test-read children (without and with BCG scar), the estimated ARTI rates when estimated by different methods (anti-mode, mirror-image and mixture model) varied between 1.9% and 2.5%. BCG-induced tuberculin sensitivity was not found to influence the ARTI estimates, as the differences in estimates between children without and with BCG scar were not statistically significant.

CONCLUSION

TB control efforts should be further intensified to reduce the risk of tuberculous infection.

Utilization of RNTCP services in rural areas of Bellary District, Karnataka, by gender, age and distance from health centre

BACKGROUND

Knowledge on utilization pattern of RNTCP shall provide important inputs towards its strengthening in rural areas.

AIMS

To find out the utilization of RNTCP services by age, sex and distance from residence to designated microscopy centres and treating health centres.

METHODS

The study was carried out in Sandur TU of Bellary District, Karnataka. Information on age, sex and residence of persons with pulmonary symptoms and detected new sputum smear positive cases during third quarter 2003 to second quarter 2004; and their treatment outcome was obtained from the respective RNTCP records. Age and sex distribution of out-patients was collected from OPD registers of one randomly selected DMC and its PHCs.

RESULTS

A lesser number of males accessed the health care services. However, larger number of males with pulmonary symptoms and new sputum smear positive cases utilized RNTCP services than females in the ratio of 1.6:1 and 2.5:1 respectively. This was due to higher prevalence of persons with pulmonary symptoms and sputum positivity rate among males. Sputum positivity rates were also lower among the elderly. Male symptomatics and cases were on an average older than females. About 70% symptomatics and 53% cases resided at more than four kilometers from the respective DMCs and treating health centres. Treatment outcome was poorer among males with higher proportion of initial defaulters and among those residing at more than 20 kms.

CONCLUSION

There is need to make health services available to the male working population at convenient hours and to be more vigilant to screen persons with pulmonary symptoms among the elderly. Collection of sputum specimen from eligible persons may be undertaken at PHCs which may later be transported to DMC. Supervision and motivation of treatment for male TB cases and those residing more than 20 kms from the treating health centres requires to be strengthened.

Prevalence of tuberculous infection among school children in Kerala

BACKGROUND

There is paucity of information on epidemiological situation of Tuberculosis (TB) in the State of Kerala. The DOTS strategy under the Revised National Tuberculosis Control Programme (RNTCP) was introduced in the year 1998 to cover the entire State by 2002.

OBJECTIVE

To estimate the prevalence of tuberculous infection among children attending 1-4th standard in a sample of selected schools in Kerala.

METHODS

A cluster-sample school-based tuberculin survey was carried out in 70 schools selected by a two-stage sampling procedure. A total of 4821 children (including those with and without BCG scar) in the age group of 5-9 years were tuberculin tested using 1 TU PPD RT23 with Tween 80 and the maximum transverse diameter of induration was measured about 72 hours later. About 81% of the children were found to have BCG scars. Analysis was also undertaken by mixture model.

RESULTS

While 67% of children without BCG scar and 62% with scar did not elicit any induration at the test site, the mode or anti-mode of reactions due to infection with tubercle bacilli could not be identified from the distribution graphs. Analysis by mixture model also did not provide the best fit thus precluding estimation of prevalence of infection. About 5% of children had reactions > or =10 mm, 3% had reactions > or =12 mm and 2% had reactions > or =14 mm.

CONCLUSION

Low proportion of reactors indicated a low level of transmission of infection in Kerala. Considering the problems in interpretation of tuberculin survey data, it may not be feasible to use ARTI as an epidemiological parameter to monitor future trends of TB situation in the state.

Annual risks of tuberculous infection in East Nusa Tenggara and Central Java Provinces, Indonesia

SETTING

East Nusa Tenggara (NTT) and Central Java Provinces, Indonesia.

OBJECTIVE

To estimate the average annual risk of tuberculous infection (ARTI) among school children aged 6-9 years in each province.

METHODS

Children attending Classes 1-4 in 65 schools in NTT and 79 in Central Java, selected by two-stage sampling, were intradermally administered 2 tuberculin units of purified protein derivative RT23 with Tween 80 on the mid-volar aspect of the left forearm. The maximum transverse diameter of induration was measured 72 h later. The analysis was carried out among 5479 satisfactorily test-read children in NTT and 6943 in Central Java. One hundred and fifty-five new sputum smear-positive pulmonary tuberculosis (PTB) cases (78 in NTT and 77 in Central Java) were also tuberculin tested. Based on the frequency distribution of reaction sizes among the children and PTB cases, the prevalence of infection was estimated by the mirror-image method using the modes of tuberculous reactions at 15 and 17 mm.

RESULTS

Using the 15 mm mode, ARTI was estimated at 1% in NTT and 0.9% in Central Java. Using the 17 mm mode, ARTI was estimated at 0.5% in NTT and 0.4% in Central Java.

CONCLUSION

Transmission of tuberculous infection may be further reduced by intensification of tuberculosis control efforts.

Health seeking and knowledge about tuberculosis among persons with pulmonary symptoms and tuberculosis cases in Bangalore slums

SETTING

Bangalore city slums, India.

OBJECTIVES

To ascertain 1) health-seeking behaviour patterns in persons with pulmonary symptoms; 2) pathways followed by pulmonary tuberculosis (PTB) cases until diagnosis and treatment; and 3) their knowledge about TB-symptoms, cause, mode of transmission, diagnosis and treatment.

METHODS

In selected slums, persons with pulmonary symptoms identified during house visits and residents with PTB were interviewed using pre-tested, semi-structured questionnaires. Visits to relevant health centres were made to obtain information regarding their treatment.

RESULTS

About 50% of the 124 persons with pulmonary symptoms interviewed had taken action for relief; of these, three quarters had first approached private health facilities. About 19% had undergone sputum microscopy and 27% chest X-ray. Of 47 PTB cases interviewed, 72% first approached private health facilities; about 50% visited two health facilities before diagnosis and 87% visited two or more facilities before initiating treatment; 42 initiated treatment at government health facilities and five who initiated treatment at private health facilities were later referred to government health facilities. The majority of persons with pulmonary symptoms and PTB cases had poor knowledge about TB, and most of those with pulmonary symptoms were not aware of the availability of free anti-tuberculosis services at government health facilities.

CONCLUSION

Educational interventions targeted at slum dwellers and their health providers are needed.

Change in the risk of tuberculous infection over an 8-year period among schoolchildren in Bangalore City

SETTING

Bangalore City, South India.

OBJECTIVE

To estimate the trends in transmission of tuberculous infection.

METHODS

Two tuberculin surveys were carried out among children attending grades 1 and 2 of 60 selected schools at an interval of 8.3 years, corresponding to the period of DOTS expansion. Tuberculin testing was carried out using 1 tuberculin unit (TU) of purified protein derivative (PPD) RT 23 with Tween 80, and the maximum transverse diameter of induration was recorded about 72 h later. As the reactions due to infection with tubercle bacilli could not be clearly delineated from cross-reactions on the frequency distributions of tuberculin reaction sizes at either survey, the prevalence of tuberculin reactions > or = 10 mm, > or = 12 mm and > or = 14 mm in size were compared between the two surveys. The annual risk of tuberculous infection (ARTI) was computed from the estimated prevalence of reactions > or = 14 mm in size.

RESULTS

Estimates of prevalence of reactions at all chosen cut-off points were lower at Survey II compared to Survey I. These differences were statistically significant. An average per annum decline in ARTI of about 4% was observed between the two surveys.

CONCLUSION

Tuberculosis control measures should be further intensified to enhance the rate of decline in transmission of infection.

Annual risk of tuberculosis infection in West Sumatra Province, Indonesia

OBJECTIVE

To estimate the annual risk of tuberculosis infection (ARTI) among children attending elementary school Classes I-III in West Sumatra Province, Indonesia.

METHODS

The survey was designed to estimate ARTI among children, irrespective of BCG scar status. Fieldwork was carried out in 72 schools selected by two-stage sampling. Children were administered 2 TU of purified protein derivative RT23 with Tween 80 intradermally on the mid-anterior aspect of the left forearm. The maximum transverse diameter of induration was measured at about 72 h. Analysis was carried out among 5653 satisfactorily test-read children aged 6-9 years.

RESULTS

The estimation by mirror-image method among all children (without and with BCG scar) revealed an ARTI of between 1% and 1.3%. The estimated ARTIs among children without and with BCG scar varied between 0.8-1.3% and 0.9-1.4%, respectively, using the mirror-image method, anti-mode method and mixture model.

CONCLUSION

Tuberculosis control efforts need to be intensified to reduce the risk of transmission of infection.

Measuring tuberculosis burden, trends, and the impact of control programmes

The targets for tuberculosis control, framed within the United Nations' Millennium Development Goals, are to ensure that the incidence per head of tuberculosis is falling by 2015, and that the 1990 prevalence and mortality per head are halved by 2015. In monitoring progress in tuberculosis control, the ultimate aim for all countries is to count tuberculosis cases (incidence) accurately through routine surveillance. Disease prevalence surveys are costly and laborious, but give unbiased measures of tuberculosis burden and trends, and are justified in high-burden countries where many cases and deaths are missed by surveillance systems. Most countries in which tuberculosis is highly endemic do not yet have reliable death registration systems. Verbal autopsy, used in cause-of-death surveys, is an alternative, interim method of assessing tuberculosis mortality, but needs further validation. Although several new assays for Mycobacterium tuberculosis infection have recently been devised, the tuberculin skin test remains the only practical method of measuring infection in populations. However, this test typically has low specificity and is therefore best used comparatively to assess geographical and temporal variation in risk of infection. By 2015, every country should be able to assess progress in tuberculosis control by estimating the time trend in incidence, and the magnitude of reductions in either prevalence or deaths.

Annual risk of tuberculous infection in Andhra Pradesh, India

BACKGROUND

There is paucity of information on epidemiological situation of Tuberculosis (TB) in Andhra Pradesh. The DOTS strategy under the Revised National Tuberculosis Control Programme (RNTCP) was introduced in the year 2000 to cover the entire State by 2005.

OBJECTIVES

To estimate the prevalence of tuberculous infection among children 5-9 years of age and to compute the average Annual Risk of Tuberculosis Infection (ARTI) from the estimated prevalence.

METHODS

A cluster-sample house-based tuberculin survey was carried out in a representative sample of children between 5-9 years of age. The clusters were selected by a two-stage sampling procedure. At first stage, five districts were selected by probability proportional to population size (PPS) method. Depending upon child population ratio, 32 clusters allocated to each district were further sub-divided into rural and urban clusters selected by simple random sampling. A total of 3636 children, irrespective of their BCG scar status, were tuberculin tested using one TU PPD RT23 with Tween 80 and the maximum transverse diameter of induration was measured about 72 hours later.

RESULTS

The prevalence of infection estimated by mirror-image technique using observed mode of reactions attributable to infection with tubercle bacilli at 20mm was 9.6% (95% CI: 8.0-11.2). The ARTI was computed at 1.4% (95% CI: 1.1-1.6).

CONCLUSION

Survey findings indicate a fairly high rate of transmission of tubercle bacilli.

Tuberculosis epidemiology in India: a review

High prevalence and incidence of disease and a high rate of transmission of infection characterise the tuberculosis (TB) situation in India. Disease surveys conducted in different parts of the country since the 1950s have reported prevalences of smear-positive pulmonary TB (PTB) of 0.6-7.6 per 1000 population, culture-positive TB of 1.7-9.8 and culture and/or smear-positive TB of 1.8-12.7. The incidence of smear-positive PTB has been observed in the range of 1.0-1.6/1000 and that of culture-positive PTB 1.0-2.5/1000 in the limited number of studies carried out. The annual risk of tuberculous infection (ARTI) had been estimated at 1-2% for most of the tuberculin surveys carried out in different areas over different time periods. During a nationwide study in 2000-2003, the average ARTI in the country was estimated at 1.5%. An increasing trend has been observed in human immunodeficiency virus (HIV) seropositivity among TB cases, which has been found to vary between 0.4% and 28.8% in different studies conducted mostly at tertiary health care centres. The proportion of new cases with multidrug resistance (MDR) was relatively low, at 0.5-5.3%. However, the proportion of MDR cases among previously treated cases varied between 8% and 67%.

Annual risk of tuberculous infection in four defined zones of India: a comparative picture

SETTING

Twenty-six selected districts in India.

OBJECTIVES

To estimate the average annual risk of tuberculous infection (ARTI) in four defined zones in the country.

STUDY DESIGN

A tuberculin survey was conducted in selected clusters of 26 districts in four defined zones of India. Children 1-9 years of age were subjected to tuberculin testing with ITU PPD RT23 with Tween 80, and the maximum transverse diameter of induration was measured 72 h later. Prevalence of infection was estimated using the cut-off point method (Method I) and the mirror-image technique (Method II) among children without bacille Calmette-Guérin scar. Results from individual zones have been reported earlier, and the results from all four zones are presented here as a consolidated summary.

RESULTS

The ARTI computed from estimated prevalence was found to be lowest in the southern zone (Method I: 1.1%, Method II: 1.0%). It was higher in the eastern zone (1.3% by both methods) and highest in the western (Method I: 1.8%, Method II: 1.6%) and northern zones (1.9% by both methods). The proportion of infected children was found to be significantly higher in urban than in rural areas in all zones.

CONCLUSION

The intensified tuberculosis control efforts need to be sustained for many years.

Average annual risk of tuberculous infection in India

Estimates of the prevalence of tuberculous infection among children 1-9 years of age were available for four defined zones of India from a recently concluded tuberculin survey. These were pooled together and the average annual risk of infection in the country was computed as 1.5%. It was higher in urban areas, at 2.2%, than in rural areas, at 1.3%. The results call for further intensification of tuberculosis control activities, especially in urban areas, greater involvement of private practitioners and information, education and communication (IEC) for high-risk groups, to reduce the diagnostic and treatment delay thereby reducing the transmission of infection in all settings.

Tuberculin sensitivity among children vaccinated with BCG under universal immunization programme

A tuberculin survey was conducted among 45988 children with BCG scar and 54227 children without BCG scar between 1-9 years of age and residing in selected rural areas of three defined zones of India. About 45-60% of the BCG-vaccinated children elicited reactions < 5 mm in size and about 70-80% had reactions < 10 mm. Therefore, in the majority of children (showing tuberculin reaction of < 10 mm), BCG-induced tuberculin sensitivity does not interfere with interpretation of tuberculin test. The study also revealed that a proportion of reactions among BCG vaccinated children in 5-9 mm, 10-14 mm and 15-19 mm range may be attributable to BCG vaccination. Therefore, reactions between 10-14 mm and especially 15-19 mm among the vaccinated children must be interpreted carefully. However, 19 mm was observed as the upper limit for BCG induced tuberculin sensitivity and all reactions >- 20 mm in size may be considered to be due to infection with tubercle bacilli, irrespective of the BCG vaccination status.

Can BCG-vaccinated children be included in tuberculin surveys to estimate the annual risk of tuberculous infection in India?

SETTING

Selected villages in three defined zones of India.

OBJECTIVES

To compare the estimated prevalence of tuberculous infection among children with and without bacille Calmette-Guérin (BCG) scar.

STUDY DESIGN

During a nationwide tuberculin survey, 1-9-year-old children were tuberculin tested using 1TU-PPD RT23 with Tween 80.

RESULTS

In the 5-9 year age group, subgroups of tuberculous infected children could be seen as distinct humps among those with or without BCG scar, but not in those aged 1-4 years. In children aged 1-4 years, the estimated prevalence of infection was respectively 3.5%, 3.8% and 3.6% among children without BCG scar, and 4.8%, 4.7% and 4.5% among children with BCG scar in the western, northern and eastern zones. In those aged 5-9 years, the estimated prevalence was respectively 10.4%, 11.0% and 9.1% among children without BCG scar and 11%, 11.9% and 8.7% among children with BCG scar in the three zones. Thus, in children aged 1-4 years, the estimated prevalence among those with BCG scar was considerably higher than in those without BCG scar. This difference was small in those aged 5-9 years.

CONCLUSION

Tuberculin surveys may be conducted irrespective of BCG scar status among children aged 5-9 years, when BCG vaccination is given using Danish 1331 strain during infancy under the Expanded Program of Immunization.

Protective effect of BCG among children vaccinated under universal immunization programme

A case-control study was conducted to estimate the protective effect of BCG vaccination against tuberculosis among children. The children with suspicion of tuberculosis (TB) attending two hospitals in Bangalore city were registered into the study and subjected to detailed clinical examination and investigations. The presence of BCG scar was taken as evidence of vaccination. Modified Stegen-Jones scoring method was adopted for diagnosing TB. The hospital children with score of 7 were considered as TB cases. Children residing in the neighbourhood of cases were similarly investigated and those scoring 4 were labeled as controls. A total of 118 age-sex matched case-control pairs were identified and final analysis was confined to 113 cases and 109 controls after excluding children with doubtful BCG scar. A low protective effect of BCG vaccination at 31% (not significant, statistically) was observed against TB - all forms combined, among children vaccinated as under Universal Immunization Programme. Though the protective efficacy against extra-pulmonary TB was observed to be higher than for pulmonary TB, it was also not significant, statistically. It will be appropriate to conduct further studies on protection rendered by BCG vaccination against tuberculous meningitis and other severe forms of TB. Besides, the quality of vaccination programme including cold chain maintenance also needs to be evaluated.

The annual risk of tuberculous infection in the eastern zone of India

SETTING

Rural and urban areas of eight selected districts in the eastern zone of India.

OBJECTIVES

To estimate the annual risk of tuberculous infection (ARTI).

STUDY DESIGN

A community-based, cross-sectional tuberculin survey was conducted among children aged 1-9 years residing in a sample of rural and urban areas. Stratified two-stage cluster sampling was adopted for selection of rural and urban clusters. A total of 40964 children in 515 clusters underwent tuberculin testing and reading with 1TU PPD RT23 with Tween 80; the maximum transverse diameter of induration was measured about 72 h after the test.

RESULTS

A bacille Calmette-Gúerin (BCG) scar was observed in 51.5% of the test-read children. The frequency distribution of tuberculin reaction size among 19332 children without BCG scar was found to be bimodal, with the mode of reactions attributable to infection with tubercle bacilli at 20 mm. The prevalence of infection was estimated as 6.9%. The ARTI computed from the estimated prevalence was 1.3%. Children residing in the urban areas were found to be at a significantly higher risk of infection than those residing in rural areas.

CONCLUSION

The high rate of ARTI in the eastern zone of India suggests a need for committed, sustained action in provision of quality tuberculosis control services.

The annual risk of tuberculous infection in Orissa State, India

SETTING

Rural and urban areas of eight selected districts of Orissa State, India.

OBJECTIVES

To estimate the average annual risk of tuberculous infection (ARTI) in the state.

DESIGN

A community-based, cross-sectional tuberculin survey was conducted among children aged 1-9 years residing in a sample of rural and urban areas of eight districts of Orissa State. A stratified sampling was adopted for selection of clusters. Highly trained designated tuberculin testers administered 0.1 ml (1 TU) of PPD RT 23 with Tween 80 by the Mantoux method to 10 626 children. Transverse tuberculin reaction sizes were measured about 72 h later by trained designated tuberculin readers. The number of children satisfactorily test-read was 10 191.

RESULTS

Based on the frequency distribution of tuberculin reaction sizes, the average ARTI in the state was estimated at 1.7-1.8%. The children residing in urban areas were observed to be at a significantly higher risk of infection than those in rural areas.

CONCLUSION

The study in Orissa State suggests high rates of transmission of tuberculous infection and calls to attention the need for intensification of concerted and sustained tuberculosis control efforts.

Estimation of annual risk of tuberculosis infection (ARTI) among children aged 1-9 years in the south zone of India

OBJECTIVE

To estimate the annual risk of tuberculosis infection (ARTI) among children aged 1-9 years in the south zone of India.

SETTING

The survey was carried out in a representative sample of villages and census enumeration blocks of towns in four south Indian states, as a part of a nationwide tuberculin survey.

DESIGN

Six districts were selected through systematic random sampling. Four hundred and twenty rural clusters and 180 urban clusters were selected from these districts on the basis of the rural-urban ratio in the entire zone. To obtain the required sample of 12,000 children without bacille Calmette-Guérin (BCG) vaccination, 51,000 had to be covered. Eighty-five children from each cluster were tuberculin tested and read for reaction sizes. The ARTI was computed from the estimated prevalence of TB infection among children without a BCG scar.

RESULT

Among 52,951 children registered for the study, 50,846 (96%) had a tuberculin test result. The BCG coverage for the study population was about 65%. Among 17,811 children without a BCG scar, the prevalence of infection was 5.9% (95%CI 4.0-7.7%); the corresponding ARTI was 1.0% (95%CI 0.7-1.4%) [correction].

CONCLUSION

The estimated ARTI for the south zone is 1.0%, as compared to the national average of 1.7% used for programme evaluation. This baseline information should be useful for the assessment of future trends.

Annual risk of tuberculous infection in Khammam a tribal district of Andhra Pradesh

A tuberculin survey to estimate annual risk of tuberculosis was conducted in Khammam tribal district during 2001-2002. A total of 8637 children were test-read--2991 without BCG scar and 5442 with BCG scar. The tests were performed using ITU PPD RT23 and the maximum size of induration was recorded at about 72 hours after the test. Based on the frequency distribution of reaction size, cut-off point for infection with tubercle bacilli was considered at 12 mm. Using this criterion, the prevalence of infection was estimated at 11.8% among children without BCG scar and 10.6% among children with BCG scar. This difference was found to be statistically insignificant. ARTI rates computed from the prevalence estimates among children without and with BCG scar were 1.6% and 1.5% respectively. It was computed as 1.5% from the prevalence in the combined group i.e. irrespective of BCG scar status.

Annual risk of tuberculous infection in the western zone of India

SETTING

Rural and urban areas of six selected districts in the western zone of India.

OBJECTIVES

To estimate the annual risk of tuberculous infection (ARI).

DESIGN

A community-based, cross-sectional tuberculin survey was conducted among children aged 1-9 years residing in a sample of rural and urban areas of six districts in the western zone of India. Stratified two-stage cluster sampling was adopted for selection of rural and urban clusters. A total of 48473 children in 600 clusters underwent tuberculin testing with 1TU PPD RT23 with Tween 80; the induration was measured about 72 h after the test.

RESULTS

The BCG scar was observed in 52% of the test-read children. Estimation of the prevalence of infection was based on the frequency distribution of tuberculin reaction size among 22259 children without BCG scar. Reactions > or = 15 mm were considered attributable to infection with tubercle bacilli. The prevalence of infection was estimated to be 9.3%, and the ARI computed from the estimated prevalence was 1.8%. The proportion of infected children was found to be significantly higher in urban than in rural areas.

CONCLUSION

The high rate of ARI in the western zone of India calls for further intensification of tuberculosis control efforts.

Annual risk of tuberculous infection in rural areas of Uttar Pradesh, India

SETTING

Rural areas in Uttar Pradesh, the most populous state in India.

OBJECTIVES

1) To estimate the average annual risk of tuberculous infection (ARI), 2) to study ARI trends with age, and 3) to compare tuberculin reactions among children with and without BCG scar.

STUDY DESIGN

A cross-sectional tuberculin survey was conducted among children aged 1-9 years residing in Rae Bareli, Hardoi and Jaunpur districts, Uttar Pradesh. Tuberculin testing was performed using 1TU of PPD RT23 with Tween 80, and indurations were measured 72 hours later. Prevalence of infection was estimated in children without BCG scar based on the cut-off point identified on the frequency distribution of reaction sizes. The ARI was computed from the estimated prevalence.

RESULTS

The proportion of children with BCG scar varied from 25% to 31% in the study districts. Using a cut-off of 14 mm among children without BCG scar, the ARI was estimated at 2.3% in Rae Bareli, 1.9% in Hardoi and 1.5% in Jaunpur, and was observed to increase with age. Tuberculin test results among children with BCG scar suggest that they may be included in tuberculin surveys to estimate ARI.

CONCLUSION

High rates of transmission of tuberculous infection suggest that tuberculosis control measures need to be intensified.

Epidemiological situation of tuberculosis in India

Epidemiological information on tuberculosis (TB) is vital for planning the control strategies in addition assessing the impact of intervention programmes. The survey findings by ICMR revealed the prevalence of sputum positive pulmonary TB is about 4 per 1000 population and an estimated 1.5 million infectious cases spreading infection in the community. Studies conducted by the National Tuberculosis Institute, Bangalore revealed similar diseases prevalence of sputum positive pulmonary TB. The annual risk of tuberculous infections defined as the probability of acquiring new infection with tubercle bacilli over a period of one year is the key parameter for the epidemiological study in developing countries. It is estimated that there are about 4.6 lakhs death in the country every year with one person dying every minute. The average annual risk of tuberculous infection is about 1.7%. The prospects of decreasing TB case now look good provided that all TB cases have access to the DOTS strategy by bringing the remaining uncovered half of the population under RNTCP.

PPD RT23 for tuberculin surveys in India

SETTING

Tuberculosis sanatoria and villages in Bangalore district.

OBJECTIVES

To study the appropriateness of continuing to use 1TU dilutions prepared by the BCG Laboratory, Guindy, in Chennai, India, from a freeze-dried form of PPD RT23 with Tween 80 received from Statens Serum Institut (SSI), Copenhagen, for tuberculin surveys in India.

DESIGN

The responses to dual tuberculin tests were compared among: 1) 63 smear-positive cases using 2TU PPD prepared by the Guindy laboratory (Dilution-G), and 2TU PPD prepared by the SSI (Dilution-S); 2) 124 smear-positive cases using 1TU and 2TU Dilution-G; and 3) 1,338 apparently healthy children using 1TU and 2TU Dilution-G. Test sites were allocated randomly using the double-blind technique. Tuberculin responses obtained during studies conducted in India and in other countries were compared.

RESULTS

The differences in sensitivity of tuberculin testing using the different preparations were found to be small and statistically non-significant. Among children, a higher proportion of reaction sizes in 10-14 mm and 15 + mm categories was observed to 2TU compared to 1TU of Dilution-G. This could reflect lower specificity of 2TU in the study area where non-specific sensitivity is highly prevalent. Studies in India and other countries do not suggest any loss in potency of 1TU PPD RT23 with Tween 80.

CONCLUSION

1TU dilutions of PPD RT23 with Tween 80 provided by the BCG Laboratory, Guindy, may continue to be used for tuberculin surveys in India.

Annual risk of tuberculous infection in the northern zone of India

OBJECTIVE

To estimate the annual risk of infection with tubercle bacilli in the northern zone of India.

METHODS

A community-based cross-sectional tuberculin survey was conducted among children aged 1-9 years who lived in a sample of villages and urban blocks of six selected districts in a defined north zone of India. A two-stage cluster sampling method was used to select rural and urban clusters. A total of 48 624 children in 598 clusters were subjected to tuberculin testing with one tuberculin unit (1 TU) of PPD RT23 stabilized with Tween 80. The maximum transverse diameter of induration was measured about 72 hours after the test.

FINDINGS

Among the 48 624 test-read children, 22 064 (45.4%) had a bacille Calmette-Gu rin (BCG) scar. On the basis of the frequency distribution of tuberculin reaction size among 25 816 children without a BCG scar, the prevalence of infection with tubercle bacilli was estimated as 10.3%. The annual risk of infection was computed as 1.9%. The proportion of infected children was significantly higher in urban than rural areas.

CONCLUSION

The high rate of tuberculous infection in the north zone of India suggests the need for further intensification of tuberculosis control efforts on a sustained and long-term basis.

Annual risk of tuberculous infection in rural areas of Junagadh district

Paucity of epidemiological data on tuberculosis in India prompted the National Tuberculosis Institute, Bangalore to embark upon a nation-wide survey to estimate the Annual Risk of Tuberculosis Infection in different parts of the country. The survey in Junagadh district, one of the 26 districts drafted under the nation-wide survey is reported here. The prevalence of infection from the analysis of 3164 children not displaying scars of the BCG vaccination was 4.16% (CI: 3.17-5.14) and from this data the ARI was computed as 0.73% (CI: 0.55-0.91). The inclusion of vaccinated children into the study group yielded similar results. The estimate of the ARI in Junagadh district is lesser than that in several other parts of India which is probably in consonance with its better socio-economic development.

Tuberculin test

Although tuberculin test is widely used for detection of tuberculous infection among children, there is no clear understanding about its performance and interpretation. This article has been written with the purpose of elucidating the performance and interpretation of standard tuberculin test, based on the experiences gained at the National Tuberculosis Institute, Bangalore and other centres. The standard tuberculin test involves intradermal injection of '1TU PPD RT23 with Tween 80' on the mid-volar aspect of forearm and measurement of the maximum transverse diameter of induration after 3 days. Larger the size of induration, higher is the probability of it being due to tuberculous infection. The majority of reactions with induration size of 15 mm and above are attributable to infection with tubercle bacilli, irrespective of BCG-vaccination status. While indurations of less than 5 mm indicate absence of any kind of tuberculin sensitivity, the majority of indurations in 5-9 mm range are usually of non-tuberculous nature. An induration of 10-14 mm requires more careful interpretation. It is more likely to be attributable to infection with tubercle bacilli in case of history of contact with smear positive case or among children with clinical findings of tuberculosis. However, the size of induration in an infected child may be diminished in the presence of immuno-suppressive conditions. One should also consider the purpose of the test while interpreting the test results.

Effect of gossypol on domestic fowl, Gallus domesticus

Domestic fowls (Gallus domesticus) were administered gossypol (10 mg/kg body weight/day) by oral intubation for 15 weeks. Drug treatment did not have any effect on body growth rate. The drug treatment, however, caused a marked decrease in the weights of testis and epididymis. Predominant changes in the histoarchitecture of testis (desquamation of germinal epithelium and inhibition of spermatogenesis) were observed following gossypol treatment. Epididymal tubules in gossypol treated animals were devoid of spermatozoa. Gossypol treatment had no effect on hematological parameters (total erythrocyte count, total leucocyte count, hematocrit and hemoglobin) studied in the present investigations.

Inhibition of liver alcohol dehydrogenase and ethanol metabolism by 3-substituted thiolane 1-oxides

3-Substituted thiolane 1-oxides (methyl, n-butyl, n-hexyl, and phenyl) were prepared and tested as inhibitors of horse, monkey, and rat liver alcohol dehydrogenases and of ethanol metabolism in rats. These compounds inhibit alcohol oxidation in an uncompetitive manner with respect to ethanol as a varied substrate. Lengthening the alkyl substituent increased the inhibitory potency because of tighter binding in the hydrophobic substrate binding pocket of the alcohol dehydrogenases. Thus, the 3-hexyl derivative was the most potent inhibitor of the purified rat liver alcohol dehydrogenase, with a Kii value of 0.13 microM. The 3-butyl derivative was the best inhibitor of ethanol metabolism in rats, with a Kii value of 11 mumol/kg. The acute toxicity in mice of the butyl derivative was 1.4 mmol/kg. Since high concentrations of alcohol do not prevent the inhibitory effects of these compounds, they may be particularly useful for preventing poisoning by methanol or ethylene glycol.

Inactivation of horse liver alcohol dehydrogenase by modification of cysteine residue 174 with 3-bromopropionic acid

Horse liver alcohol dehydrogenase is inactivated with Michaelis kinetics at pH 7 and 25 degrees C by 3-bromopropionic acid. In the absence of NAD+, the Ki is 2 mM, and the pseudo bimolecular rate constant (k3/Ki) is 0.03 M-1 s-1; in the presence of 1 mM NAD+, Ki is 2.3 mM, and k3/Ki is 0.006 M-1 s-1. 3-Bromopropionic acid is a competitive inhibitor, Ki of 0.4 mM, against ethanol as a substrate. Inactivation was prevented in the ternary complexes with NAD+ X pyrazole and NADH X isobutyramide, was retarded by NAD+, NADH, or bipyridine, and was almost unaffected by imidazole and AMP. Carboxyethylated enzyme did not detectably (as observed spectrophotometrically) bind bipyridine, NAD+, or NADH. Enzyme was inactivated with radioactive 3-bromopropionic acid, aminoethylated, and digested with trypsin and chymotrypsin. Analysis of the labeled peptides showed that Cys-174 was predominantly modified. In the presence of 1 mM NAD+, the reaction was much less specific. The interaction of the carboxyl group of 3-bromopropionic acid with the guanidino group of Arg-369 probably facilitates the selective reaction with Cys-174, which is ligated to the zinc at the active site. Carboxyethylation apparently inactivates by interfering with the proper binding of the pyrophosphate of the coenzyme to the enzyme.