The quality of symptom elicited by health workers in an epidemiological survey on tuberculosis was

assessed by again subjecting a 10% random sample of the persons interviewed, by the supervisory staff, independently.

Three thousand four hundred and forty nine persons were thus interviewed twice. The overall estimates for overdiagnosis

and under-diagnosis in the elicitation of symptoms by health workers were to the extent of 16% and 8%

respectively, with minimal yield of sputum positivity from the discordant groups of persons. The additional load of 16%

for sputum examination can thus be considerably reduced if health workers are well trained in symptom-elicitationscreening

of the population and their work is monitored through spot supervisory checks

Gopi, P G

Govindaraj, M S

Subramani, R

NIRT Institutional Repository

QUALITY OF SYMPTOM ELICITATION IN AN EPIDEMIOLOGICALSURVEY ON TUBERCULOSISP.G.Gopi1, R. Subramani1 and M.S. Govindaraj2(Received on 2.11.1008; Accepted on 5.6.1999)Summary : The quality of symptom elicited by health workers in an epidemiological survey on tuberculosis wasassessed by again subjecting a 10% random sample of the persons interviewed, by the supervisory staff, independently.Three thousand four hundred and forty nine persons were thus interviewed twice. The overall estimates for over-diagnosis and under-diagnosis in the elicitation of symptoms by health workers were to the extent of 16% and 8%respectively, with minimal yield of sputum positivity from the discordant groups of persons. The additional load of 16%for sputum examination can thus be considerably reduced if health workers are well trained in symptom-elicitation-screening of the population and their work is monitored through spot supervisory checksKey words : Symptom elicitation, Tuberculosis survey.INTRODUCTIONIn community surveys conducted to obtainepidemiological information, like diseaseprevalence and incidence, the population isfirst screened by application of pre-determinedcriteria before case detection. The fieldinvestigator has got a target population forscreening. While eliciting the symptoms, hemay miss a real symptomatic and /or pick upan asymptomatic as a symptomatic. In theformer case, there could be a chance that a realcase is missed which results in under-estimation of the prevalence. On the latterinstance, sputum examination done for awrong person could result in overload of thework. So, it would be worth studying theextent to which the field investigators missreal symptomatics (under-diagnosis) andwrongly identify non-symptomaticsas syptomatics (over-diagnosis). With thisbackground, an exercise was carried out toassess the quality of symptoms elicited by thehealth worker (a field investigatorregisteringand screening the population) in anepidemiological survey.OBJECTIVETo estimate the proportion of symptomaticsmissed (under-diagnosis) and non-symptomat-ics wrongly identified as symptomatics (over-diagnosis) by health workers in an epiolemio-logical survey.MATERIAL AND METHODSAn epidemiological survey for surveillanceof tuberculosis was undertaken in 1990 in twopanchayat unions of Kadambathur andTiruvelangadu of Tiruvallur taluk inChingleput district (now Tiruvallur district) ofTamil Nadu. Thirty villages with a populationof about 54,000 were included in the survey.Two screening methods, namely, Symptom andX-ray were used for detection of cases. Thehealth worker visited the households andregistered all the persons aged 10 years andabove. He identified the symptomaticsusing the definition of symptomatic as adopted in theOriginal Article Ind. J. Tub. 1999, 46, 2611. Senior Research Officer; 2. Deputy Field SupervisorTuberculosis Research Centre, Epidemiology Unit, ChennaiCorrespondence : P.G. Gopi, Tuberculosis Research Centre, Epidemiology Unit, Mayor Ramanathan Road(Spurtank Road), Chetput, Chennai - 600 031.District Tuberculosis Programme (DTP) anddirected all persons for X-ray examination.During the resurvey, which was started in 1993,a routine random check was introduced in theelicitation of symptoms. The quality of thesymptoms elicited by the health worker, everyday was assessed by a senior staff member onthe same day from a random sample ofindividuals by visiting them and elicitingthe symptoms independently.Sample Size and Sampling Procedure A 10% random sample of the eligiblepopulation screened by the health worker wasincluded in the study. The sample was selectedfrom the list of persons who reported for X-ray,as directed by the technician after symptomscreening. The 10% random sample wasselected from the list in the following way:The last digit of the serial number of the firstindividual who turned up for chest X-ray, wasnoted which could be any unmber between 0and 9. A systematic sample was then taken byselecting every 10th individual starting fromthe said digit. Thus, a 10% random sample ofthe population screened every day wasobtained for re-elicitation of sysmptoms by asupervisory staff member. The persons listedfor random examination were visited at homeby a supervisory staff member who elicitedsymptoms independently and recorded themin a separate proforma in a manner similar tothat used by the health worker. The healthworker remained unaware of the identity of theindividuals cross-checked by the supervisorystaff. Similarly, the supervisory staff wasunaware of the nature and duration ofsymptoms as elicited by the health worker.Sputum was also collected from the newsymptomatics as identified by the supervisorystaff.AnalysisThe analysis was carried out on theassumption that symptoms elicited by thesupervisory staff member were more reliableand these were taken as the standard to becompared with those of the health worker inorder to find out the extent of agreement.Objective assessment of the reliability of thesupervisory staff member was not made.The random sample consisted of 3,449persons from a population of about 35, 000persons screened for the survey.RESULTSExtent of agreement between health worker andsupervisory staffTable 1 show the extent of agreementbetween health worker and supervisory staff inidentifying the symptomatics. Of the 819persons identified as symptomatics by thehealth worker, 129 (15.8%) had no symptom(over diagnosis by the health worker), aselicited by the supervisory staff. Similarly, ofthe 2630 persons identified as symptomatics bythe health worker, 204 (7.8%) had symptoms(under-diagnosis), as elicited by the super-visory staff. The proportion of symptomatics aselicited by the supervisory staff was 25.9%(894of 3449) compared with 23.7% (819 of 3449) bythe health workers. The difference wasstatistically significant (P<0.01).Extent of agreement between different health workersand supervisory staffIn all, 35 health workers screenedthe population. Of these, 6 health workers whohad screened a sufficient segment of thepopulation (at least 150) from the sample wereused for this comparison. Table 2 shows thecomparison between heath workers and thesupervisory staff in terms of over-diagnosis,under-diagnosis, accuracy and Kappa262 P.G. GOPI ET AL.    Supervisory staffSympto-         Asympto-           Totalmatics            maticsSymptomatics 690 129 819Asymptomatics 204 2426 2630Total 894 2555 3449Health workerTable I. Extent of agreement between health worker               and supervisory staff in elicitation of               symptoms.statistics. It can be observed that all the healthworkers, except Health Worker 2 performedwell in terms of the extent of agreement withthe supervisory staff.The distribution of the identified symp-tomatics in terms of duration of symptoms isgiven in Table 3. Persons having cough ofduration less than two weeks were consideredas having no cough. Of the 122 persons havingcough of duration more than two weeks to lessthan 1 month, as elicited by health worker, thesupervisory staff did not find cough in 34(27.9%) persons. Three hundred and fourpersons had cough of duration 1 month andabove, as elicited by health worker. Amongthese, only 237 (78.09%) had cough of 1 monthand above, as elicited by the supervisory staff.The over-diagnosis by health worker byhealth worker by duration of cough was to theextent of 19.2% (82of 426) and (140 of 3923)respectively.DISCUSSIONThe extent of agreement, in elicitingsymptoms, between health workers andsupervisory staff revealed over-diagnosis byhealth worker to the extent of 16% whichresulted in an additional load of sputumexamination. Similarly, under-diagnosis byhealth workers in elicitation of symptoms was8% reducing load of sputum examination inrespect of these persons. Even though over-diagnosis meant additional load of sputumexaminations, it may help in diagnosing morecases which would he missed while screeningthe population. In the case of under-diagnosis,sputum examination is not done unless theirX-ray is abnormal, calling for sputumexamination. A high proportion of under-diagnosis may cause underestimation of theprevalence of the disease.The extent of agreement between varioushealth workers and supervisory staff ineliciting symptoms in general was the same forall the health workers, in terms of accuracy andKappa statistics which adjusted for any chanceagreement between the health worker andsupervisory staff.The duration of symptoms, like cough andchest pain, varied ad elicited by health workersin comparison with supervisory staff. Amongpersons having cough of less than 1 monthduration as elicited by health worker, aboutone fourth did not have cough as elicited bysupervisory staff. Similarly, among personshaving cough of 1 month or more by healthworker, about three-fourth were correctlyTable 3.  Destribution of symptimaties by duration ofcough.1 2 3 4 5 6No. of persons screened 694 396 329 531 157 263Over-diagnosis 18.1 18.1 16.3 16.5 17.1 17.2Under-diagnosis 7.1 9.9 7.6 6.0 6.0 6.3Accuracy 90.2 88.4 90.0 91.3 90.5 91.3Kappa 73.9 67.2 75.4 77.1 75.4 75.0Validity measures(%)Health WorkersTable 2.  Extent of agreement between health workers in comparison with supervisory staff in elicitation of  symptoms. 0<2       2 weeks -       >1     Totalweeks   <1 month      month0 -<2 weeks 2883 38 102 30232 weeks -      <1 month 34 55 33 122>1 month 48 19 237 304Total 2965 112 372 3449Duration aselicited byhealthworkerDuration as elicited bysupervisory staffQUALITY OF SYMPTOM ELICITATION IN AN EPIDEMIOLOGICAL SURVEY 263categorized but another 16% did not havecough at all, as elicited by supervisory staff.However, the overall agreement (symptom vsno symptom) in eliciting cough and chestpain, irrespective of the duration wassatisfactory for health workers and super-visory staff : K= 0.72 (95% CI : 0.66-0.78).Sputum positively in the two discordantgroups (symptomatic by health worker butasymptomatic by supervisory staff andasymptomatic by health worker butsymptomatic by supervisory staff)was negligible. The overall proportion of personseligible for sputum examination based onsymptom screening by health worker is about10%, of which 16% are really asymptomaticsand sputum examination is not required forthem. Thus, the overload of sputumexamination can be reduced considerably ifthe population is screened better foridentification of symptomatics followed bytheir sputum examination. This can beachieved by supervisory staff and in-servicetraining given to them, if necessary.ACKNOWLEDGEMENTThe authors are thankful to the field team incarrying out the field work. Secretarialassistance rendered by Mr. B. Doraiswamy ishighly appreciated. The authors thank Dr. P.R.Narayanan, Director, Tuberculosis ResearchCentre, for his support and guidance.264 P.G. GOPI ET AL.

Quality of symptom elicitation in an epidemiological survey on tuberculosis

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Quality of symptom elicitation in an epidemiological survey on tuberculosis

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