Background: Under the Revised National Tuberculosis control Programme (RNTCP) in India, the designated microscopy centres (DMCs) form the basic unit of smear positive TB case detection in a district. There is a need by the programme managers to estimate the mean and range of smear positive tuberculosis (TB) cases that can be detected at DMCs located in different type of health facilities to channelize their resources. Methods: It is a cross-sectional study conducted in the state of Karnataka, India during January 2014 to December 2014 based on the compiled reports from past five years received from all the 30 districts of the state. The prediction was made based on the performance of these DMCs in the last five years using a modeling technique. Results: The proportions of the DMCs located at health facilities are Primary Health Institutions/Centres (PHIs)—73%, Tuberculosis Units (TUs)—15%, Medical colleges (MC)—7%, District TB centres (DTC)—3% and Private Practitioners (PP)—2%. The maximum number of cases that can be detected at DTC is 3621 (SD 54), TU is 9224 (SD 90), PHI is 20,412 (SD 135), PP is 859 (SD 26) and MC is 8322 (SD 84). Conclusion: The predicted values will essentially serve as a tool for the programme managers of Karnataka to plan, strategize and monitor the performance of DMCs in the state.
In India, tuberculosis (TB) continues to be a major public health problem and it accounts for 25% of global burden. To contain the same, the Government of India is implementing the Revised National Tuberculosis Control Programme (RNTCP) since 1997 [
The DMCs are spread across different type of health care facilities. Based on the population size, the programme has uniformly allotted a microscopy centre for every 0.1 million population at plain areas with an exception for tribal areas for which the population size is 0.05 million [
Despite the constant efforts by the programme there has been no drastic change in the number of smear positive TB cases detected. The district programme managers are constantly involved in evolving out the strategies which could have impact on the district smear positive TB case detection rates. There is an inherent need for a tool by the programme managers to estimate the mean and range of smear positive TB cases that can be detected at DMCs located at different type of health facilities through which they can strategize their resources and prioritize their activities to achieve the programme objectives.
We conducted this study to predict the number of smear positive TB cases that can be detected at DMCs located in different type of health facilities based on the performance of these DMCs in the last five years using a modeling technique.
Among the all smear positive TB cases detected at DMCs from Karnataka, 2009-13.
1) To determine the number (proportion) of smear positive TB cases detected at DMCs located in different type of health facilities.
2) To predict the number (quartile range) of smear positive TB cases that can be detected at DMCs from different health facilities.
It is a study conducted in the state of Karnataka during January 2014 to December 2014. The study involves the retrospective analysis of the records and reports received from the DMCs of 30 districts from the past five years. Under the programme, the monthly performance of DMCs which includes the numbers of presumptive TB cases screened and number found positive are received at district tuberculosis centre through a RNTCP reporting format called “Annexure M”. The District submits the compiled report of all its DMCs to the state regularly and the state monitors the DMCs closely for presumptive TB case examination rates, slide positivity rates, results of on-site evaluation reports and random blinded re-checking reports consistently [
Routinely, the variables collected in the reporting formats includes number of presumptive tuberculosis cases examined and found positive for diagnosis, follow-up and repeat sputum examination. However, the type of DMC like Peripheral health institution, District TB centre, Tuberculosis unit, Medical College and private practitioner are not included in the routine reporting formats.
For the purpose of this study, we included all the DMCs from the years 2009-2013. Those DMCs which had complete data were analyzed and the total number of DMCs for the following years were 2009 (645), 2010 (630), 2011 (590), 2012 (563) and 2013 (645). The data on the type of health facility were collected from the districts based on their locations. They were classified as 1) District TB centres (DTC) 2) Medical Colleges (MC) 3) Peripheral health institution (PHI) 4) Tuberculosis unit (TU) 5) Private Practitioners (PP). Further, the DMCs were analyzed for number of presumptive TB cases examined for diagnosis and smear positive TB cases detected among those examined at all type of health facilities.
A model was constructed using normal probability distribution; we considered this model because the type of data which is dealt was discrete. As per Bernoulli trial, in a screening test, a smear positive case is considered as success while a negative case is considered as a failure. Hence, in order to predict the chances of occurrence of “x” number of positive cases, bernoulli probability law (Bernoulli distribution) is applicable [
The normal probability law is calculated using the following formula [
f ( x ; μ , σ ) = P [ X = x ] = 1 σ 2 π e − ( x − μ ) 2 2 σ 2
Considering, the smear positive TB case as a success and smear negative as a failure; the chances of occurrence of success has been estimated and prediction over number of positive cases has been made. The normal probabilities have
been calculated using the following transformation: Z = X − n p n p q , where Z is the
standard normal variable having mean zero (0) and standard deviation unity (1), “X” is the projected number of positive cases (number of successes) at which probability is to be calculated, np is the mean (actual number of positive cases) and n p q is the standard deviation of binomial distribution such that p + q = 1.
The smear positive TB cases detected at various types of health facilities are shown in
Of all the DMCs, the proportion of the DMCs located at health facilities like PHIs is 73%, TUs is 15%, Medical colleges is 7%, District TB centres is 3% and private practitioners is 2%. All the DMCs at health facilities has a progressive trend for smear positive TB cases while the peripheral health institution and medical college DMCs has steep rise in detection with increasing presumptive TB case detection. The best fit line has a narrow confidence interval which predicts the accuracy of the estimates.
Based on the model, the number of smear positive TB case detected at probabilities of P0, P25, P50, P75, P100 with mean and standard deviation at DMCs in various health facilities are shown in
Types of Health facilities | P0 (0%) | P25 (25%) | P50 (50%) | P75 (75%) | P100 (100%) | P (Mean) | SD |
---|---|---|---|---|---|---|---|
DTC | 3200 | 3370 | 3407 | 3444 | 3621 | 3407.0 | 54.78 |
TU | 8523 | 8813 | 8873 | 8935 | 9224 | 8873.4 | 90.10 |
PHI | 19,519 | 19,874 | 19,966 | 20,057 | 20,412 | 19,965.2 | 135.69 |
PP | 655 | 739 | 757 | 775 | 859 | 756.8 | 26.24 |
MC | 7669 | 7939 | 7995 | 8052 | 8322 | 7995.0 | 83.97 |
This is one of the first studies that predict the number of sputum smear positive TB cases detected at DMCs located in different health facilities of Karnataka based on normal probability distribution model. Accordingly, the major contributions for a smear positive TB case detection rate in a district from the DMCs are located at PHI, TU, MC, DTC and PP. The trend for the next few years might be almost consistent as the data used for extrapolation of the estimates is based on the programme data from the past five years. However, it is most unlikely to expect an increasing trend line in smear positive case detection rate until and unless there is major strategic changes in policy and implementation. The study findings have following programmatic implications.
First, the large numbers of cases are detected from the DMCs located at the PHIs, TUs and Medical colleges. The district programme managers to achieve the goal of 180 presumptive TB cases examination per lakh population with 10% - 15% slide positivity rates in the districts should concentrate their efforts on strengthening the PHI and TU DMCs. The programme managers can use the prediction values provided in the table below to calculate their performance against the predicted value for the state.
Second, at the local level the district programme managers need to develop various strategies to improve the DMCs performance. One such strategy for a DMC is “feeder” strategy which helps in ensuring all those presumptive TB chests symptomatic from other feeding PHCs are routed to the DMC without missing any of the referred cases. The information technology (IT) enabled systems to monitor the human resources, the logistics and the patient flow from the feeder PHCs to DMCs will possibly increase the quality of supervision and monitoring which will have direct effect on case detection rate. Inadvertently, the general health system strengthening has to happen in terms of quality of health services provided at the PHCs which will draw all sections of people for health services utilization. The programme needs to customize its advocacy, communication and social mobilization activities based on the DMC laboratory data while it should also conduct surveys that could gather information from the communities’ perspective to increase the utilization of laboratory services.
Third, introduction of available newer technologies like fluorescent microscopes at PHCs level and cartridge based nucleic acid amplification test at tuberculosis units will help in increasing the yield of smear positive TB cases. However, to garner the evidence the programme may conduct feasibility and cost effectiveness studies before proposing a change in a policy.
To accomplish the targets as mentioned by the “End TB strategy”, the programme certainly has to take bold steps [
We declare that we have no conflicts of interest.
The idea was conceived by SBN, SS, GS, JPT, SMK, AS and SC. The authors have contributed in writing and approving the final manuscript.
Nagaraja, S.B., Shastri, S., Tripathy, J.P., Sharma, G., Kunjathur, S.M., Singarajipur, A. and Chadha, S. (2017) Prediction of Smear Positive TB Cases at Different Types of Designated Microscopy Centres, Karnataka, India. Journal of Tuberculosis Research, 5, 258-264. https://doi.org/10.4236/jtr.2017.54027