The role of chest radiography in patients presenting with anterior chest

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Journal of the Royal Society of Medicine Volume 81 November 1988

The role of chest radiography in patients presenting with anterior chest pain to the Accident & Emergency Department

N J Russell BChir MRCP C F A Pantin PhD MRCP P A Emerson MD FRCP N J Crichton PhD Department of Thoracic Medicine, Westminster Hospital, London SWiP 2AP Keywords: chest pain; chest X-ray; Accident & Emergency Department

Summary The chest radiological findings and outcomes of 120 consecutive patients attending the Accident & Emergency Department with anterior chest pain were recorded prospectively to investigate the value of routine chest radiography in their management. Twenty-one patients (17.5%) were excluded because of incomplete information. Thirty-seven radiological abnormalities were identified in 33 (33%) of the remaining 99 chest X-rays. Seventeen of the abnormalities identified in 14 (14%) ofthe chest X-rays were clinically significant. The casualty officer's interpretation of 70 (70%) of the chest X-rays was correct, but 36 errors were made interpreting the other 29 chest X-rays. Of these errors, 19 were false negative errors, resulting in the mismanagement of two patients and 17 false positive errors, resulting in the mismanagement of four patients. It appears that a routine chest X-ray provides little information of practical value in the management of patients with anterior chest pain attending an Accident & Emergency Department, unless the training of medical students and junior doctors in the interpretation of chest X-rays is improved. Introduction The commonest presenting medical complaint of patients attending the Accident & Emergency Department (A&E Dept) at this hospital is anterior chest pain; in 1984 it occurred in 5.5% of all cases and 25% of medical cases. It has become the practice to request a standard postero-anterior chest radiograph on virtually all such patients, yet the value of this test in this context is unproven. This study examines this use of radiological facilities and also the accuracy with which the casualty officers interpret the chest X-rays.

0141-0768/88/

110626-03/$02.00/0 1988 The Royal Society of Medicine

Methods The A&E Department of the Westminster Hospital treats approximately 26 000 patients per year and is staffed by 5 senior house offlcers in Accident & Emergency, supervised by a resident medical offlcer (registrar grade) under the direction of a Professor of Surgery. From December 1984 to October 1985, the decisions made about the diagnosis and management of all patients aged 16 years or over who presented to the Westminster Hospital A&E Dept with anterior chest pain were audited prospectively. The casualty officers recorded their diagnoses, their interpretations of the standard postero-anterior chest X-ray and the electrocardiogram (ECG) and their management decisions concerning the patient on a special form accompanying the casualty card. Expected patients, discussed in advance by their general practitioner

with the admitting medical registrar, were excluded from the study. All patients presenting with chest pain, who were not admitted were offered a follow-up appointment within one week of their attendance at the A&E Dept at a clinic conducted by one of us. The history and the results of the physical examination were recorded on a structured form; further investigations, such as repeat chest X-rays, ECGs, cardiac enzymes and exercise testing were ordered as clinically indicated. Those patients who did not attend for a personal interview were sent a postal questionnaire, or interviewed using a structured form over the telephone. If information was missing, the patient's general practitioner was contacted. Those patients admitted to hospital were interviewed before discharge and the results of the relevant investigations were recorded. A retrospective diagnosis on each patient was made independently by two assessors on the basis of the collected data, using pre-determined diagnostic criteria. Such disagreements that occurred between the first two assessors were settled by consultation with a third assessor who was a consultant cardiologist. This paper reports the audit of the interpretation of the chest X-rays, taken on consecutive patients presenting to the A&E Dept with chest pain in the 2 months of December 1984 and January 1985. The chest X-rays were reported independently by the two main assessors and their agreed opinions checked against the report from the Radiology Department. Those radiological abnormalities which would have contributed either to the diagnosis or to the management of patients were noted. The assessor's diagnoses and their chest X-ray reports were then compared with those made by the 5 casualty officers when the patient first attended. Senior radiologists were always available to the casualty officers, during normal working hours, if they decided that a second opinion was necessary. During the study period the casualty officers did not seek a second opinion for any of the chest X-rays. Results Patient characteristics and follow-up During the study period of 63 days, 120 patients were eligible for inclusion; only 2 patients had to be excluded because the casualty officer did not complete the form. Follow-up information was obtained on 114 of the remaining 118 patients. This was by interview after admission in 45 patients; by telephone or postal questionnaire in 32; by interview at the follow-up clinic in 31 and by information from their general practitioner, or from another hospital or further

Journal of the Royal Society of Medicine Volume 81 November 1988 Table 1. Final diagnosis in 118 patients with anterior chest pain Number

Diagnosis

39 38 33 5 2 1

Cardiac Chest wall pain Functional Oesophagitis/dyspepsia Pleurisy Pneumothorax

attendant at the Westminster A&E Dept in the remaining six. There were 91 males and 27 females with mean age 50.5 years (SD±17 years). The final diagnoses of all the 118 patients are shown in Table 1. Chest X-ray characteristics Nineteen of the 118 patients had to be excluded because no chest X-ray was obtained in the A&E Dept. However, 11 had a chest X-ray taken within the next seven days. Three showed an abnormality, 2 of which were minor (old pulmonary tuberculosis; cardiomegaly with a pacing box), but one was significant (pneumonitis) in that if it had been recognized on first attendance, the clinical management would have been different. All the chest X-rays taken ofthe remaining 99 patients were technically satisfactory and 33 showed one or more abnormalities. In 4 instances there were 2 abnormalities on the same chest X-ray, that the total number of abnormalities seen was 37, 17 of which were considered to be of some clinical significance (Table 2). so

The casualty officers' diagnoses of the chest pain The casualty officers misdiagnosed 33 of the 118 patients with regard to their chest pain. The management errors (total 19) resulting from these mistakes were unnecessary referrals (9 cases), inappropriate drug prescribing (8 cases), and inappropriate discharge from the A&E Dept (2 cases).

Casualty officers' interpretation of chest X-rays The casualty officers correctly interpreted 70 of the 99 chest X-rays, but made 36 errors in the interpretation of the remaining 29 chest X-rays. Table 3 lists the false negative errors. The casualty officers failed to recognize 19 radiological abnormalities

in 17 ofthe abnormal chest X-rays. Knowledge

of 6 of these 19 missed abnormalities was considered to be directly relevant to the diagnosis and/or management of 4 of the patients. Thus, the casualty officers missed 6 of the 17 clinically significant radiological abnormalities and 13 of the 20 clinically irrelevant abnormalities; the difference between these proportions is not statistically significant (x2=3.25; P>0.05). Table 4 lists the false positive errors. In 16 chest X-rays the casualty officers incorrectly identified 17 abnormalities which the assessors decided were not present. Four of these false positive errors proved clinically significant in that two patients were given unnecessary antibiotic therapy and 2 patients were unnecessarily referred to an outpatient clinic. In 4 instances, a casualty officer not only failed to recognize a radiological abnormality that was there, but also reported a non-existent abnormality on the same chest X-ray. These 4, therefore, feature in both Tables 3 and 4.

Table 2. Chest radiological abnormalities in 99 patients presenting with anterior chest pain, showing also those instances in which the abnormality contributed to diagnosis or management

Type of X-ray abnormality

Number of cases in which radiological Number of abnormality CXRs contributed to with this diagnosis or abnormality management

Cardiomegaly Pulmonary oedema Old pulmonary tuberculosis Pleural thickening Old rib fracture

5 5 5 4 3 2 2 2

Fresh rib fracture Pleural effusion Pulmonary fibrosis Linear opacity Diaphragm abnormalities Bone metastases Pulmonary infiltration Pneumothorax Bronchiectasis Hyperinflation Total

2 2 1 1 1 1 1 37

1 5 1 0 0 2 2 2 0 0 1 1 1 1 0 17

Table 3. Missed radiological abnormalities (false negative errors) in 99 patients with anterior chest pain, showing also those in whom the radiological abnormality was clinically significant Number of missed Number of abnormalities chest X-rays' contributing to abnormalities diagnosis or missed management Old pulmonary tuberculosis Old rib fracture Pleural thickening

3 3 3

0

Cardiomegaly

2

0

Bone metastases Pulmonary infiltration Fresh rib fracture Pleural effusion Pulmonary fibrosis

Diaphragm abnormalities Linear opacity Hyperinflation Total

1

1 1 1 1

1 0

1 1 1 1

1

1

0

1

0

1

0

19

6

Table 4. Non-existent radiological features diagnosed by casualty officers in 99 patients with chest pain (false positive errors)

Number of false positive errors Localized pulmonary shadowing Bilateral pulmonary shadowing Discrete pulmonary opacity Pulmonary oedema Pleural thickening Fresh rib fracture Totals

7 4 2 2 1 1 17

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Journal of the Royal Society of Medicine Volume 81 November 1988

A similar proportion of radiological errors was made by each of the 5 casualty officers - 21%, 23%, 27%, 38% and 39%; none of the differences between the percentages reach statistical significance (P>O.l:x2 test). As would be expected, wrong clinical diagnoses were made by casualty officers in a significantly higher proportion of patients (17/29: 59%) when the chest X-ray was interpreted incorrectly than when it was interpreted correctly (16/70: 23%) (X2=11.8: P< 0.001). However, only 2 management errors of importance were a direct consequence of missed radiological abnormalities. In one patient, diffuse pulmonary fibrosis was overlooked and in the other, rib metastases and malignant pulmonary infiltration were attributed to technical inadequacies. These errors were all recognized and remedied by the regular X-ray department auditing system that operates in the department. Discussion These results highlight some of the difficulties that are experienced by relatively junior casualty officers when interpreting the chest X-ray films of patients complaining of anterior chest pain. Other studies have shown that clinically significant errors in chest X-ray interpretation are amongst the commonest committed by casualty officers when viewing all types of X-ray1'2. In our selected group of X-rays, interpretational errors were made in 29%. It is interesting to note that nearly as many false positive mistakes were made (17) as were false negatives (19), suggesting that casualty officers may have difficulty in recognizing the full range of radiological normality in the chest. From Table 4, it will be seen that the commonest false positive error was to mistake normality for either localized or generalized pulmonary shadowing. Although such errors are unlikely to have any serious clinical implications, they may lead to unnecessary treatment or referral, as occurred in 4 of the 16 instances in this study and this does generate undue anxiety for the patients. More important are the false negative errors in which radiological abnormalities are missed. In our study, only 2 of the false negative errors can be said to have led to serious management errors - one in which a patient with malignant rib and pulmonary infiltration was discharged, and one in which diffuse pulmonary fibrosis was overlooked. In the 29 patients in whom the chest X-ray was misinterpreted, there were 17 incorrect clinical diagnoses of the cause of the chest pain, whereas in the 70 patients in whom the chest X-ray was correctly interpreted, there were only 16 incorrect clinical diagnoses. Although this

suggests that radiological errors contribute to errors in the clinical diagnosis of the chest pain, in many instances the radiological error was independent of the diagnostic error (for example, overlooking old rib fractures has no relevance to angina misdiagnosed as dyspepsia). It is reassuring that the majority of false negative errors were trivial (Table 3) and that of the 14 abnormal chest X-rays which had contributed to clinical management, 10 were interpreted correctly by the casualty offlcers. This study did not take into account the value of a normal chest X-ray in excluding an abnormality which the casualty officer thought probable. Thus, the number of clinically useful chest X-rays performed probably exceeded the number of chest X-rays in which clinically significant abnormalities were noted. Clinically relevant abnormalities were present in 14% ofthe X-rays which is an acceptable positive pickup rate for a routine test. However, if casualty officers misinterpret 29% of the chest X-rays of patients with chest pain, then the test is providing less useful information than expected. These results reinforce the proposal made elsewhere, that A&E Depts should keep a comprehensive selection of chest X-rays to allow new casualty officers to familiarize themselves with commonly missed features, and also with the full range of radiological normalityl'2. The development of clinical guidelines for selective radiography, as has been suggested for patients attending the A&E Dept following trauma3, may help to reduce the proportion (86%) of chest X-rays which do not contribute to the clinical management of the patient. Acknowledgments: NJR and NJC were supported by a grant from BUPA. Our gratitude is extended to the staff of the Westminster A&E Dept for their co-operation during the study. References 1 Carew-McColl M. Radiological interpretation in an Accident and Emergency Department. Br J Clin Pract 1983;37:375-8 2 Wardrobe J, Chennells PM. Should all casualty radiographs be reviewed? Br Med J 1985;290:1638-40 3 Gleadhil DNS, Thomson JY, Simms P. Can more efficient use be made of x-ray examinations in the accident and emergency department? Br Med J 1987;24:943-7

(Accepted 9 March 1988. Correspondence to Dr Russell, Hyptertension Unit, Clatterbridge Hospital, Bebington, Wirral, Merseyside. Dr Pantin is now at the Respiratory Physiology Unit, City Hospital, Stoke-on-Trent. Dr Crichton is now at the Department of Statistics, University of Exeter, Exeter, Devon)