Is routine pre-entry chest radiograph necessary in a high tuberculosis prevalence country?

CONTEXT: Chest radiographs have been used worldwide as a screening tool before employment and training, by various healthcare and other government and nongovernment institutions. Many studies done in the past have demonstrated a relatively low yield for tuberculosis detection and therefore, the authors have questioned this practice. AIMS: To compare the value of the preadmission/employment chest radiograph in two groups, namely, those who have been previously exposed to a healthcare setting (post-exposure group) and those who have not been exposed (pre-exposure group) and to determine if there is a significant difference in tuberculosis detection between these two groups. SETTINGS AND
DESIGN: A retrospective review of the reports of the chest radiographs of all candidates appearing for admission to various undergraduate and postgraduate courses in our institute between 2014 and 2017 was performed.
MATERIALS AND METHODS: The various abnormalities detected were recorded and the findings in the two groups were compared. STATISTICAL ANALYSIS USED: Chi-square test was used to compare between two group proportions.
RESULTS: Thirty out of 4333 (0.69%) candidates in the pre-exposure group and 53 out of 3379 (1.57%) candidates in the post-exposure group showed abnormalities on chest radiographs involving the lung parenchyma, mediastinum, heart, or pleura. In the pre-exposure group, six (0.14%) were found to have underlying cardiac disease and one (0.02%) had tuberculosis. Among the six candidates in the post-exposure group who underwent further investigations in our institute, five (0.15%) were diagnosed to have tuberculosis. Although there was no statistically significant difference in tuberculosis detection between the groups (P = 0.051), there is a trend towards higher detection of tuberculosis in the post-exposure group.
CONCLUSIONS: In a country where the prevalence of tuberculosis is high, the pre-employment chest radiograph may still have a role in detecting tuberculosis in the post-exposure group.

Introduction

Plain radiographs are being used worldwide as a screening tool for assessing the health status of candidates before their employment/admission as trainees in various institutions. However, this practice should be “evidence-based”.[1234] There are previous publications from different parts of the world, debating the utility of chest radiographs as a routine screening tool.[2356789] A recent publication from India found that of all the pre-employment chest radiographs (CXR) done, only 0.58% required further evaluation based on findings on the chest radiograph and of this only 0.17% required further treatment. Thus, concluding that pre-employment chest radiographs should be restricted to symptomatic individuals to help decrease background radiation, as well as reduce cost and time involved.[10] However, there is a paucity of data on the role of the pre-employment chest radiograph for tuberculosis (TB) screening in India, a high TB prevalent country.

There are two groups of candidates who seek admission to medical colleges - one that has not previously trained in a healthcare setting, in undergraduate programs and another that has been trained in a healthcare setting, mostly seeking admission to postgraduate programs. Our study aimed to assess the value of the preadmission/employment chest radiograph in a high tuberculosis prevalence country, especially for people with occupational exposure to tuberculosis. We hypothesize that a pre-employment chest radiograph can detect significantly more cases of pulmonary tuberculosis in people previously exposed to a healthcare setting (post-exposure group) in comparison to people who have not been exposed (pre-exposure group).

Subjects and Methods

Approval was obtained from the Ethics committee/ Institutional Review Board and a waiver of consent was obtained. This was a retrospective study of the data recorded from CXRs of all candidates who applied for admission and were selected for interviews to various undergraduate and postgraduate courses between the years 2014 and 2017 at tertiary care teaching hospital in south India. The candidates were categorized into two groups; the first group constituted those applying for undergraduate medical, nursing, and allied science programs, who had not previously been exposed to a healthcare facility hence, we called them pre-exposure group (pre-EG) and the second, those applying for postgraduate medical or nursing courses, who had previously been exposed to the hospital environment, we called them post-exposure group (post-EG). The reports of the chest radiographs taken at the time of the medical examination were reviewed by an experienced radiologist and the abnormalities were systematically recorded on a data sheet. If abnormal radiographic findings had triggered further investigations, the details of the further investigations performed were reviewed and the results were analyzed.

Statistical analysis

A comparison of the proportion of abnormalities between the two groups was done using the Chi-square test. All analyses were done at a 5% level of significance. Statistical analysis was performed using SPSS version 16.0 for Windows (SPSS, Chicago, IL).

Results

A total of 7712 chest radiographs were included in the study involving male and female candidates >=17 years of age and less than 40. The age of the candidates in the pre-EG group was 17–18 years with only <1% being older and none above 25 years of age. This group included a few who had completed a basic degree program in a non-healthcare center. The age of the candidates in the post-EG group was between 20 and 40 years and all these candidates had at least 2 years of training at a healthcare setting.

Table 1 summarizes the abnormalities seen in both groups. The radiographic abnormalities were categorized as under chest wall or skeletal, cardiovascular (including evidence of previous cardiac surgery), lung parenchyma, mediastinal and hilar, pleural, diaphragmatic, and miscellaneous abnormalities. The chest wall, skeletal, and diaphragmatic abnormalities including those with cervical ribs, bifid ribs, elongated transverse processes, mild scoliosis, pseudoarthrosis of the ribs, posterior spinal fusion, and old fracture of the clavicle/ribs, diaphragmatic hump, and diaphragmatic eventration were deemed to be incidental and not specifically recorded.

Table 1

Summary of the abnormalities seen on chest radiographs in both groups of candidates

	pre-EG	post-EG	P
Total number of candidates	4 333	3 379
Number of candidates with all abnormalities (lung parenchyma, pleural, cardiac, mediastinal)*	30 (0.69%)	53 (1.57%)	0.002
Number of candidates with lung parenchymal, pleural and mediastinal abnormalities	14 (0.32%)	44 (1.30%)	<0.001
Abnormalities requiring further investigations	18 (0.42%)	20 (0.59%)	0.272
Abnormalities confirmed on further investigations†	7 (0.16%)	13 (0.38%)	0.055
Number of candidates with a final diagnosis of tuberculosis	1 (0.02%)	5 (0.15%)	0.051

*Refer to Table 2 for a detailed list of abnormalities. †Refer Table 3 for the list of abnormalities confirmed on further investigations. pre-EG: Pre-exposure group. post-EG: Post-exposure group

A significantly larger number of candidates in the Post-EG group had cardiovascular abnormalities than in the pre-EG group (P = 0.002) [Table 2]. Those who had significant abnormalities underwent further investigations, which included computed tomography (CT), ultrasound, ECG (electrocardiogram), and ECHO (echocardiogram) as appropriate to further characterize the abnormality. The candidates who did not require further investigations included asymptomatic candidates who had findings such as calcified granulomas, postinflammatory change, increased bronchovascular markings, pleural thickening, diaphragmatic eventration, sternotomy sutures due to prior cardiac surgery (atrial septal defect [ASD])/ventricular septal defect [VSD] closure) and situs inversus.

*Table 2

Cardiovascular, lung parenchyma, mediastinal and pleural abnormalities detected on chest radiographs in the pre- and post-exposure groups

Abnormality	pre-EG	post-EG
Cardiovascular	16	9
Lung parenchymal abnormalities
Postinflammatory change	2	4
Pulmonary nodule	1	2
Calcified granuloma	2	15
Cavitary lesion	0	1
Increased bronchovascular markings	1	1
Parenchymal opacity	2	7
Retrocardiac density	3	0
Total (lung parenchymal abnormalities)	11	30
Mediastinal and hilar adenopathy	0	8
Pleural pathology
Pleural thickening	0	3
Pleural effusion	0	1
Blunted CP angles	3	2
Total (pleural pathologies)	3	6

preEG: Pre-exposure group, postEG: Post-exposure group, CP: Costophrenic

Seven (0.16%) candidates of the 18 in the pre-EG were confirmed to have clinically significant abnormalities on further investigation. [Table 3] One candidate had left upper zone infiltrates on the chest radiograph which was diagnosed to be tuberculosis. The remaining six candidates had various cardiac abnormalities as mentioned in Table 3.

Table 3

Abnormalities confirmed on further investigations in the pre- and post-exposure groups

Group	Chest radiographic abnormality	Final diagnosis
pre-EG	Left upper zone infiltrates	Tuberculosis
	Cardiomegaly	Anemia with splenomegaly
	Cardiomegaly	Severe mitral regurgitation
	Cardiomegaly	Atrial septal defect
	Cardiomegaly	Mitral valve prolapse with severe mitral regurgitation
	Prominent pulmonary bay	Patent foramen ovale
	Prominent pulmonary bay	Left ventricular hypertrophy
post-EG	Widened right paratracheal stripe - mediastinal adenopathy	Tuberculosis
	Left upper zone cavity	Tuberculosis
	Ill-defined opacity in the right lung apex	Tuberculosis
	Widened right paratracheal stripe - mediastinal adenopathy	Tuberculosis
	Left pleural effusion	Tuberculosis
	Mild cardiomegaly	Multiple ventricular premature complexes

pre-EG: Pre-exposure group. post-EG: Post-exposure group

In the post-EG, of the 20 (0.59%) who underwent further evaluation with ECHO, CT, or other laboratory investigations; 13 (0.38%) were found to have significant abnormalities warranting further invasive investigations. Five of the candidates with lung parenchyma, mediastinal and/or hilar adenopathy and pleural effusion who underwent further investigations (two mediastinal node FNAC, one pleural biopsy, and two bronchoalveolar lavages) in our institute, were diagnosed to have tuberculosis [Table 3]. The remaining seven candidates chose not to undergo further investigations in our institute and did not report back but their imaging findings suggest the likelihood of pathology including tuberculosis.

Discussion

The screening of applicants to training programs as well as pre-employment screening is an important duty of the employer, primarily to evaluate the potential health risks to the patients who seek care in the healthcare center and to the employees.[11] In a high TB prevalence country like India, screening for active TB is an important exercise.

A study comparing three different methods of pre-employment medical evaluations in 2008 concluded that the self-administered questionnaire evaluated by an occupational physician is the preferred method of pre-employment evaluation for nonhazardous occupations.[12]

Most of the studies evaluating the role of pre-employment chest radiographs among healthcare workers concluded that it should not be a routine procedure but should be used in those at higher risk.[131415] A review of the chest radiograph reports of 416 staff, performed in a teaching hospital in Nigeria also concluded that its use should be limited to older job seekers as the only abnormality reported was cardiomegaly that was seen in ~66% of those aged >=41 years.[1] Studies performed in other non-healthcare centers also came to similar conclusions.[89]

Unwarranted radiation exposure was one of the main reasons given in a detailed report from the state of California in 2006, concluding that routine pre-employment chest radiographs were unnecessary.[6] Only 2.8% of 1021 cases showed findings suggestive of pulmonary TB in a prospective study conducted before admission to a Nigerian university.[16] Two other studies from Africa also concluded that routine chest radiographs as screening tools for active pulmonary tuberculosis be reconsidered due to poor diagnostic yield.[1718]

However, a few large studies from Taiwan and Africa concluded that a routine pre-employment screening CXR is of significant value especially in countries with high TB prevalence. In Taiwan, they found that the mandatory pre-employment screening programs had a much better yield than the existing national TB surveillance program.[19] A retrospective review of 2540 CXRs in Africa among young male applicants as laborers in factories or bus drivers found 2% of active pleuropulmonary tuberculosis cases, hence concluding that in their situation, considering the well-known relationship of tuberculosis with the existing HIV/ AIDS pandemic, the screening CXR should be retained in the pre-employment screening of candidates.[20]

An article in 2017 reviewing the various guidelines on pre-employment medical examination available on the databases of PubMed, EMBASE, and Google scholar concludes that the job description should guide the content and scope of a pre-employment medical examination and due to the lack of adequate scientific basis, employees should not be subjected to unnecessary investigations.[21]

The QuantiFERON-TB Gold test is a cost-effective screening tool for tuberculosis which is also more specific when compared with the previously used tuberculin skin test. However, in our country, with the increased availability of radiographs including digital radiographs with its better image quality, lower running costs, and lower radiation dose; the chest radiograph is a more effective screening tool in comparison with a test like the QuantiFERON-TB Gold which is more expensive and not as freely available.

Our study is rather unique, as we have compared the findings on CXRs in both pre-EG and post-EG groups and this has not been previously done in other studies.

In our study, we find that among the various abnormalities on the CXRs seen in both pre-exposure and post-exposure groups, cardiac disease was more commonly seen in the pre-EG and lung parenchyma and mediastinal disease was more common in the post-EG.

Pulmonary tuberculosis is a well-known occupational disease among healthcare professionals at all levels.[22] A high prevalence of pulmonary tuberculosis in our country puts healthcare workers at a high risk of the disease warranting early detection and treatment for the safety of the individual and that of the patients.[23] Candidates applying for post-graduate courses have already been exposed to the medical environment and are thus at higher risk of developing pulmonary tuberculosis among other infections. The predominant abnormality seen in the pre-EG was a cardiac disease with only one candidate having lung parenchymal changes of tuberculosis. This reiterates the fact that candidates who have been previously exposed to a hospital environment are at greater risk of developing tuberculosis.

In the pre-EG, we can presume that some of these candidates who may be from varied backgrounds and socioeconomic status are for the first time undergoing a detailed complete health screening and this could explain the higher number of cardiac abnormalities detected in this group. As the expertise of the clinician examining the candidate may vary, the chest radiograph may have a role in alerting the clinician to a cardiac abnormality that may have otherwise been missed. Therefore there may be some value in screening this population. Whereas in the post-EG group, the screening was more effective, picking up tuberculosis which could pose a serious hazard to the patients and other healthcare personnel in the hospital.

The retrospective nature of the study is a limitation, as only the reports of the chest radiographs were reviewed and not the films themselves. Any significant findings on the radiographs could not be reviewed as they were not available at the time of the study.

Conclusion

Our study has a large sample of subjects in both the pre- and post-exposure groups and is unique in addressing “routine” preadmission/employment chest radiograph. Given the fact that there appears to be a higher TB detection in the group with prior exposure to a healthcare setting, the pre-employment chest radiograph may still have a role in this group.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.