Case-Finding and Related Issues in Tuberculosis

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Title: Case-Finding and Related Issues in Tuberculosis
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NT! Bulletin 1995,31/3&4,48-53

Case-Finding and Related Issues in Tuberculosis
VK Chadha & DB Deshmukh

Introduction

'T’uberculosis is one of the most widespread infections
A ever known to man, as one-third of world's population
is infected with M.tuberculosis1. In India more than a
million people die of tuberculosis each year and nearly
one-fourth of estimated 12 million tuberculosis patients
are infectious2. While people of all ages suffer, the
heaviest toll is in productive age group leading to adverse,
social and economic consequences. Demographic changes
and epidemic of human immunodeficiency virus (HIV)
are expected to further increase the burden of
tuberculosis3.

Early detection of cases by an efficient case-finding
programme followed by optimum treatment constitute the
most important control measures. Though, National
Tuberculosis Programme (NTP) formulated on the basis of
sound epidemiological, sociological and operational
studies, is in operation in the country for the past three
decades, the disease continues to be a major public health
problem.

This paper examines various aspects of case-finding
and aims at providing suggestions for improving the
efficiency of case-finding activities.

Role of Case-Finding in Tuberculosis Control
Case-finding is defined as a well organised and
systematic effort to discover largest possible number of
cases in the community on a continuous basis in an
acceptable, practicable and cost-effective methodology
using simple and standardized tools.
The objective of case-finding is to identify sources of
infection in the community and thus for the purpose of
tuberculosis control, a case is an individual discharging
tubercle bacilli in the sputum (bacteriologically positive
on culture). Among them, in about 50%, bacilli can be
demonstrated by direct microscopy4 (smear positive
cases) and the rest are smear negative culture positive
*

Epidemiologist, National Tuberculosis Institute, 8. Bellary Road.
Bangalore-560 003.

** Medical Officer, District Tuberculosis Centre, Yavatrnal,
Maharashtra.

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cases. Under NTP, a case is defined as the one who is
smear positive and a patient with radiological evidence of
tuberculosis but smear negative is called suspect.
The District Tuberculosis Programme (DTP) has the
potential of detecting about 40% of the prevalent
bacteriological cases5. This is considerably higher than the
observed rate of incidence of the disease which is onethird of the prevalence4.

To make favourable epidemiological impact on the
tuberculosis situation, cases equivalent to 85% of
case-finding potential of DTP must be cured after
detection. Though improving cure rates is important,
improvement of case-finding efficiency has been shown to
be more crucial6 in improving the overall efficiency of
DTP.

World Health Organization (WHO), in its new global
strategy for control of tuberculosis has recommended
detection of 70% of all smear positive cases and cure rate
of 85% to be achieved every year in developing
countries1.

Priority in Case-Finding
It is well known that smear positive cases are more
dangerous as a source of infection of tuberculosis and they
are also the ones who have the worst prognosis7. Smear
negative culture positive patients come next in regard to
both the factors. In the developing countries, with
resources for tuberculosis control being limited, priority
should be given for diagnosing and treating smear positive
cases. Emphasis on case-finding is more in rural areas as
75% of cases reside in these areas, the prevalence rate
being same as in the urban areas8.

Reliability and Acceptability of
Case-Finding Tools
In a situation where many diagnostic tests are available,
the choice of tools for case-finding depends upon their
reliability, acceptability, applicability and cost. Tools
available for diagnosis of tuberculosis are discussed here
under:

i)

Culture examination of sputum specimen is
considered at present as the gold standard for
assessing reliability of other tools since its
sensitivity and specificity is close to 100%.
However, the technique of processing sputum for
culture and its examination requires highly
trained staff and sophisticated equipments
installed al enormous cost. It takes about lour to
six weeks to detect tubercle bacilli. This could
result in delay in starting treatment and some
patients may be lost in the intervening period. The
cost of detecting a case by culture alone was
found to be several times higher than the cost of
detecting a smear positive case by direct
microscopy9. Additional cost of retrieving the
patient when results of culture are available,
makes it unavailable to be employed routinely for
case-finding activities, even though the reliability
of tool is quite high.

experience of the staff. With proper training and
supervision by an experienced Laboratory
Technician from District Tuberculosis Centre
(DTC), health workers of general health
institutions could become highly proficient in
direct sputum microscopy9. Operational studies
on case-finding have shown that on an average,
only one sputum is required to be examined per
PHI per day5. Moreover, treatment can be started
immediately. About 84% of smear positive cases
presenting at PHls can be detected by
examination of two sputum specimens . As the
additional case yield from more than two
specimens is not commensurate with the cost
involved, NTP recommends two smear
examinations before labeling a patient as smear
negative. The cost of detecting a case by smear
examination is found to be one-fourth of that by
culture examination 9 .

ii)

Radiological examination of chest though
highly sensitive, has low specificity and hence
patients diagnosed only on the basis of X-ray are
called suspects. Interpretation of X-ray films is
difficult with high degree of inter and intra-readcr
variation. Even in a situation when interpretation
of X-ray films of those voluntarily reporting to an
urban clinic with chest symptoms of more than
four weeks duration was made by two
independent readers and an umpire reader for
disagreed films, X-ray was found to have a
predictive value of 62% with 88% sensitivity and
96% specificity10. This means that 38% of those
diagnosed by X-ray did not have tuberculosis.
Moreover, the patient cannot be put on treatment
immediately. Higher initial cost and difficulty in
maintenance are also other major obstacles for its
use in developing countries, especially in rural
areas.

iv) Screening of symptomatics The ‘Awareness
Study’19 revealed that 95% of the
bacteriologically positive cases were aware of
one or more symptoms and 50% of them seek
relief of their symptoms at the nearest general
health institutions.

Cough alone or in association with other
symptoms has been found to be present in almost
all chest symptomatics attending PHls5. Most of
the cases could be diagnosed by screening
patients self-reporting at PHls for complaints of
cough for more than two weeks duration and
subjecting them to direct microscopy5. One out of
every ten such patients was found to be smear
positive.
Use of chest symptoms as a screening tool has
been observed to be highly sensitive in an urban
centre10 as 95% of the cases diagnosed were
among chest symptomatics.

ii) Sputum microscopy is less sensitive than X-ray
but enough to detect the most dangerous sources
of infection and is highly specific. The predictive
value of 82 to 95% was observed with 80%
sensitivity and 99% specificity when chest
symptomatics of more than four weeks were
subjected to smear examination at an urban
clinic10. Therefore, fewer false positive cases
were put on treatment than by X-ray. The
predictive value of a single smear examination
among symptomatics at Peripheral Health
Institutions (PHls) varied from 64 to 87% . In
actual practice, the efficiency of diagnosis by
microscopy depends on skill, aptitude and

Since symptomatic screeningj has a low
specificity10, it cannot be used alone as a
case-finding tool.
v)

Newer diagnostic methods Newer culture
methods such as BACTEC allow more rapid
detection of growth in about 1-2 weeks. But these
methods arc more expensive and not widely
applicable in our situation. Tests based on
Polymerase Chain Reaction (PCR) by
amplification of a segment of DNAcan detect just
a few bacterial cells in a sputum specimen within
a few days. These tests arc still in the process of
standardisation and at best may substitute for

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culture and sensitivity testing in national
reference laboratories and also it may not be
possible to use these as a routine diagnostic tool.
Serological tests based on detection of
mycobacterial antigens and antibodies have
shown mixed results and find little application in
a routine mycobacteriological laboratory.

Under NTP, the patients attending PHIs on their own
volition are screened for presence of chest symptoms and
symptomatics among them are subjected to direct
microscopy. Since patients attending DTCs are mostly
chest symptomatics, they are screened by mass miniature
radiography and those with any X-ray abnormality are
examined by smear microscopy. The predictive value of
this strategy of case-finding is found to be very high20 and

On perusal of merits and demerits of different
diagnostic tools, it can be seen that sputum
microscopy is the most appropriate tool for
case-finding under programme situations in our
country.

hence passive case-finding methodology has been adopted
under NTP.

Case-Finding Strategy

Quality Control of Case-Finding Tools

On an average 2.5% of out-patients attending PHIs are
chest symptomatics and one out of every 10 sputa
examined are positive for AI B on direct microscopy5. The

The choice of case-finding strategy has been a
contentious issue in the past.

case-finding efficiency of individual
monitored against this background.

In mass case-finding surveys, the entire community is
required to be screened by X-ray and those with shadows
suggestive of tuberculosis are subjected to sputum
examination. When mass case-finding surveys were
repeated either at one year interval or at 3 months
interval13, similar incidence rates were observed. This
suggests that cases appear all through the year in the
community and mass surveys carried out at intervals fail
to pick up all these cases. In an operational study by (he
National Tuberculosis Institute (NTI), Bangalore, mass
surveys in the community resulted in a poor case yield14.

It is very important to control the quality of techniques
used in case-finding especially in PHIs. In a study11 by
NTI, the sputum smears prepared from symptomatics at
peripheral microscopy centres were re-examined at the
Institute. There was an under-diagnosis of 18% and
over-diagnosis of 2.8% at centres when compared to
results of re-examination. This suggests the need for
development of a system of re-examination. Alternatively
more intensive training and supervision is recommended
to reduce this gap. The microscopes must meet the
technical standards for proper smear examination and
maintained accordingly. Sufficient number of sputum cups
and microscopic slides should be made available and reuse
of slides for microscopic examination is to be

More cases were discovered among self-reporting chest
symptomatics at health institutions than mass surveys
conducted at intervals of three years in Czechoslovakia15
and one year in Japan16. High operational cost'1, poor case
yield and low predictive value prompted WHO to
recommend that case-finding by mass surveys should be
abandoned17.

Examination of contacts cannot be recommended as a
case-finding
method.
Neither
epidemiological
considerations nor the case yield18 justify its use.
However, WHO17 recommends examination of contacts
only if they have symptoms.

Sputum camps at best can be a periodic effort and not
only result in diversion of skilled staff but also dissuade
the community from seeking care at regular service
centres.
Cases found by any of the active methods of
case-finding are unlikely to comply with treatment. The
symptoms of tuberculosis develop soon after the onset of
disease10-13 prompting the patients to seek medical advice.
About 50% of the cases contacted general health services
for relief of their symptoms19 and this group included
most of the smear positive cases5.

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PHIs can

be

discontinued.
Since a small number of sputa arc examined in PHIs,
WHO holds the view that it may be difficult to maintam
high quality of smear examination in such institutions
and a dedicated sputum microscopy facility should be
established for every one lakh population backed up by
adequate supervision. Currently, this strategy is being tried
as pilot projects.

In the case of X-ray examination, quality of X-ray
picture is to be evaluated and independent dual reading of
X-ray films is recommended to reduce over and
under-reading.
Proper recording and reporting will help in improving
quality of case-finding, retrieval of cases and evaluation of
case-finding activities.

Delay in Case-Finding

The patient’s alertness to the symptoms of tuberculosis
leading to proper action combined with readiness of health

services in making a correct diagnosis play an essential
role in case-finding. Even if patients are conscious of the
symptoms, social stigma, fear of expenses, lack of faith in
quality of health services and long distance to the health
centres discourage the patients from seeking medical care.
In Korea22, a median delay of 1.8 months by the patients
has been observed in visiting a health facility after
development of symptoms with 30% of them being
diagnosed after 6 months. Many patients with symptoms
suggestive of tuberculosis are either overlooked23 because
of inadequately trained staff or missed by poor quality of
sputum examination. Diagnostic delay, an important
indicator of quality of a tuberculosis programme, of one
month has been observed even in the well functioning
programme of Japan24 and is expected to be much longer
in developing countries. Transmission of infection
continues in the prediagnosis period and epidemiological
impact of treatment programme is nullified to a great
extent.
Constraints in Case-Finding
While DTP has not yet been introduced in as many as
20% of the districts in the country, a significant proportion
of PHIs still remain to be implemented as only 56% of
available health institutions have been implemented so far.
Though DTCs have achieved a case-finding efficiency of
71%, the same under Pills has remained low at 36%. The
smear positivity rates al PHIs have remained low27 al less
than 5% of the specimens examined against the
expectation of 8%. This aspect needs to be examined
further whether the expected positivity rates arc higher or
the quality of sputum microscopy is below par.

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The entire central budget is allocated only for drugs
and no funds have been earmarked for procurement of
diagnostic equipments and maintenance. Non-utilisalion
of personnel trained by NTI and lack of adequately trained
medical and para-medical personnel, especially in PHIs,
insufficient supply of basic materials, chemicals and
reagents, improper recording and reporting and inadequate
supervision from DTC are some of the important
constraints in implementation of an efficient case-finding
and treatment programme.

especially for identification of persons with cough of more
than two weeks, which is found to be present in 70% of
tuberculosis patients19, during their routine domiciliary
visits needs the attention of health administrators.
More than one-third of cases were observed to seek
relief outside the government health set up even in a rural
area25. The patient with chest symptoms undergoes many
tests and sputum microscopy is not asked for. The
diagnosis of tuberculosis is pronounced on the basis of
X-ray results, ESR and mantoux test. Many practitioners
are not alert to the possibility of tuberculosis and this
results in cases being diagnosed in late stage. Therefore, it
is of great importance to bring general practitioners under
the ambit of NTP after imparting adequate knowledge
about its various aspects.

Non-Governmental Organizations (NGOs) should be
involved in mass education activity to create awareness
among general public, convincing funding agencies that
this is a programme worthy of financial support and
influencing government legislators on the need to give due
priority Io tuberculosis control activities.

Research Issues in Case-Finding

— Patient and community behaviour after development
of symptoms and extent cum reasons of delay in
case-finding need to be determined.
— Development of more reliable, simple, rapid and
inexpensive methods for identifying cases is
required.
- Identification of risk factors in tuberculosis will help
to determine those most likely to develop active
tuberculosis.

— In longitudinal study at Bangalore, 13% ol smear
negative patients progressed to become smear
positive26. Moreover, as a result of HIV epidemic,
the clinical spectrum of tuberculosis may be altered.
Therefore, research is needed to make more reliable
diagnosis of smear negative pulmonary tuberculosis.

— Methods of private sector collaboration with NTP
need Io be demonstrated.

Approaches for Improving Case-Finding

Conclusion

Case-finding efficiency today is at a low ebb and on an
average, only one-third of the potential is being achieved
under DTI’. New approaches for reducing the gap between
case load and case-detection need to be evolved.

While the strategy of tuberculosis case-finding
formulated after sound operational research has a
reasonable potential, the case-finding activity under NTP
is at a low ebb. For too long, focus has been solely on
chemotherapy, the full potential of which can only be
realised after reducing the gap between case-finding

Case-finding activity especially at I’HIs is at a low
level and utilisation of Multi-Purpose Workers (MPWs),

51

*

potential and current level of case-finding efficiency.
Though the need for a more reliable and efficient
case-finding tool cannot be denied, for the time being it is
essential to continue relying on sputum microscopy which
is practical and cost-effective and can be provided in all
parts of developing countries.
DTPs should be implemented in all the districts and all
health institutions in the country including remotest areas
should be covered with tuberculosis case-finding and
treatment programmes.

Quality of case-finding has to be upgraded by providing
medical personnel and health workers trained in proper
selection of chest symptomatics, sputum collection and
examination. Standard microscopes with provision of
proper maintenance, adequate supply of sputum cups and
slides, use of quality reagents, proper recording and
reporting aided by adequate supervision of PHIs by DTC
personnel will enhance the efficiency of case-finding
programme.
Adequate treatment of diagnosed cases by
uninterrupted free supply of drugs and case-holding
resulting in high cure rates will boost public faith in the
community towards the services provided. Mass education
campaigns in collaboration with NGOs to convince the
public about curability of disease will help to remove
social stigma. General public should be made aware of the
symptoms of disease and availability of services in order to
increase their utilisation. Messages about sputum
microscopy being the most reliable means of diagnosing
tuberculosis will help to generate demand for the same.

Guiding private practitioners about the techniques of
case- finding followed by treatment and their involvement
as also that of other health agencies like CGHS, ESI
dispensaries and hospitals, railways, defence services and
charitable institutions in case notification and submission
of reports on treatment results will widen the ambit of
case-finding under DTP.
Finally, the programme must be geared to treat
effectively all additional cases found by stepped up
case-finding activity in order to bring a significant
epidemiological impact on the problem of tuberculosis.

References

I. World Health Organization: The global tuberculosis
situation and the new control strategy of WHO:
Tubercle, 1991,72, I.

52

2. National Tuberculosis Institute: Facts and Figures on
tuberculosis and national tuberculosis programme,
Government of India, 2nd Edition, 1994.
3. Paul John Doi in Mario C, Raviglionc, Arata Kochi: A
review of current epidemiological data and estimation
of future tuberculosis incidence and mortality;
WHO/TB/93.173.

4. National Tuberculosis Institute: Tuberculosis in a rural
population of south India — A five year
epidemiological study, Bull Wld Hlth Org 1974, 51,
473.
5. Baily GVJ Savic D, Gothi GD & Nair, SS: Potential
yield of pulmonary tuberculosis cases by direct
microscopy of sputum in a district of south India; Bull
Wld Hlth Org 1967,37, 875.

6. Chakraborty AK. Balasangameshwara VH, Jagota P,
Srcenivas TR and Chaudhuri K: Short course
chemotherapy and efficiency variables in national
tuberculosis programme: A model; Indian J lub 1992,
39,9.

7. Jagota P & Aneja KS: Priority to sputum positive
cases under NTP - Rationale; NTI Newsletter, 1977,
14,11.
8. Indian Council of Medical Research: Tuberculosis in
India: A sample survey 1955-58; Special report series
No.3, ICMR, New Delhi.

9. Nagpaul DR, Savic DM, Rao KP & Baily GVJ:
Case-finding by microscopy; W1IO/TB/Tcchn.
Information/68.63

10. Nagpaul DR, Vishwanath MK & Dwarkanath G: A
socio-epidemiological study of out-patients attending
a city tuberculosis clinic in India to judge the place ol
specialised centres in a tuberculosis control
programme; Bull Wld Hlth Org 1970, 43, 17.
11. Rao KP. Nair SS, Naganathan N & Rajalakshmi R:
Assessment of diagnosis of pulmonary tuberculosis by
sputum microscopy in a district tuberculosis
programme; Indian J Tub 1971, 18, 10.

12. Nair SS, Gothi GD, Naganathan N, Rao KP, Banerjee
GC & Rajalakshmi R; Precision of estimates of
prevalence of bactcriologically confirmed pulmonary
tuberculosis; Indian J Tub 1976, 23, 152.
13. Gothi GD, Chakraborty AK, Parthasarathy K &
Krishnamurthy VV: Incidence of pulmonary
tuberculosis and change in bacteriological status of
cases at shorter intervals; Indian J Med Res 1978, 68,
564.

14. National Tuberculosis Institute: An operational study
of alternative methods of case-finding for tuberculosis
control; Indian J TB 1979, 26, 27.

22. Mari T, Byong Won Jin & Sung Jin Kim: Analysis of
case-finding process of tuberculosis in Korea;
Tubercle & LD 1992, 73, 225.

15. Krivinka R, Drapela J, Kubik A, Dankova D,
Krinavek J & Ruzha J: Epidemiological and clinical
study of tuberculosis in the district of Kolin,
Czechoslovakia; Bull Wld lllth Org 1974, 51,59.

23. Stott H: Centralisation and decentralisation of
case-finding activities for pulmonary tuberculosis at
district level in Kenya; WHO/TB/82-128.

16. Shimao T: Tuberculosis case-finding : A review of
case-finding methods and problems of delay in
case-finding, WHO/TB/82-131.
17. WHO Technical Report Series No.552, 1974, (ninth
report of the WHO expert committee on tuberculosis).

18. Nair SS & Gothi GD: Place of contact examination in
a tuberculosis programme; Indian J Tub 1973, 20, 164.
19. Banerjee D & Anderson S: A sociological study of
awareness of symptoms among persons with
pulmonary tuberculosis; Bull Wld Hlth Org 1963, 29,
665-683.
20. Balasangameshwara VII & Chakraborty AK: Validity
of case-finding tools in a national tuberculosis
programme; Tubercle & LD, 1993, 74, 52.

21. Personal communication. (Dr Rohit Sarin, National
Consultant, WHO, Nirman Bhavan, New Delhi).

STRENGTHENING

24. Aoki M, Mori T & Shimao T: Studies on factors
influencing patient’s, doctor’s and total delay of
tuberculosis case-detection in Japan; Bull IUAT & LD
1985,60, 128.
25. Radha Narayan, Susy Thomas, Pramila Kumari,
Prabhakar S, Ramprakash AN, Suresh T &
Srikantaramu N: Prevalence of chest symptoms and
action taken by symptomatics in a rural community,
Indian J Tub 1976, 23, 160.

26. Krishnamurthy MS, Rangaswamy KR, Shashidhara
AN &. Banerjee GC: Some aspects of changes in rural
population and fate of tuberculosis cases after an
interval of 12 years; NTI Newsletter, 1974, 11, 1.
27. Suryanarayana L, Vembu K, Rajalakshmi R &
Satyanarayana C: Performance of National
Tuberculosis Programme in 1993 : An appraisal;
Indian J Tub 1995,42, 101.

PRIMARY HEALTH CARE

i

The district is the frontline unit for planning, organizing and managing primary health care.
Programmes have to be devised by governments, the voluntary sector and communities, all planning
and working together. While considerable decentralization of authority is called for, overall national
guidance and monitoring have to be provided by government. District health systems cannot be
strengthened in isolation; the development of the whole system is essential to the functioning of the
different parts.
The holistic approach to health care will not work without determination and bold enlightened
leadership. Unfortunately, there are increasing pressures to organize resources for health along
traditional, vertical lines and to pursue goals and programmes in isolation. The organization of health
systems based on the comprehensive objectives of primary health care is difficult, and practical
experience in this area remains limited, particularly in international organizations. The sceptics who
claim that the district approach is woolly and unmanageable should become more closely acquainted
with what is going on in the field and should help to encourage joint action. Those working at
government level in developing countries should be aware that the giving of special attention to primary
health care in the district is a logical step towards health for all.

Source: Tarimo E & Fowkes FGR: Strengthening the backbone of primary health care:
Wld HI th Forum 1989, 10, 79. '

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