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Double Contrast Barium Enema Sensitivity: A Comparison of Studies by Radiographers and Radiologists
Clinical Radiology (2002) 57: 604±607 doi:10.1053/crad.2002.0952, available online at http://www.idealibrary.com on
Double Contrast Barium Enema Sensitivity: A Comparison of Studies by Radiographers and Radiologists D . G . C U L PA N , A . J . MI TC H E L L , S . H U G H E S , M. N U T M A N , A . H . C H A P M A N Department of Radiology, St James's University Hospital, Leeds, U.K. Received: 16 July 2001
Revised: 2 November 2001
Accepted: 1 December 2001
PURPOSE: A retrospective study of histologically proven cases of colorectal cancer (CRC) was performed to assess whether the sensitivity of the radiographer-performed double contrast barium enema (DCBE) diered from that of the radiologist-performed study. MATERIALS AND METHODS: Histologically proven cases of CRC were reviewed over a 3-year period to ascertain whether: the diagnosis had been made by DCBE in the 3 years before histological diagnosis; the lesion had been correctly diagnosed; the examination had been performed by a radiologist or radiographer. RESULTS: In the 3-year period there were 478 cases with histologically proven CRC. Of these, 239 (50%) had undergone DCBE as the initial radiological investigation of the colon. Sixty-four examinations had been performed by radiographers. A correct diagnosis was made in 58 cases (90.6%), the report was equivocal in one case (1.6%), there were four false-negatives (6.25%), and one case was abandoned (1.6%). One hundred and seventy-®ve examinations were performed by radiologists. A correct diagnosis was made in 157 cases (89.7%), the report was equivocal in one case (0.6%), there were 16 false-negatives (9.1%), and one case was abandoned (0.6%). CONCLUSION: A sensitivity of 90.6% for radiographer-performed studies compared favourably with 89.7% for radiologist-performed studies and supports the practice of radiographers undertaking barium enemas. Culpan, D. G. et al. (2002). Clinical Radiology 57, 604±607. # 2002 The Royal College of Radiologists Key words: barium enema, radiographer, radiologist, sensitivity, skills mix, colorectal cancer.
The practice of radiographers performing double contrast barium enemas (DCBEs) has been increasing in the U.K. over the past 8 years, since a pilot study [1] showed that examinations performed by radiographers were comparable in technical quality to those performed by radiologists. Since then, over 600 radiographers have attended a training course (Leeds Barium Enema Course for Radiographers) which was developed following the pilot study. Supervising radiologists and radiographers performing barium enemas will wish to know that standards have been maintained following the introduction of this form of skills mix. Law et al. [2], by using colonoscopy as a gold standard, reported a sensitivity for radiographer-performed barium enemas of 95% for carcinomas and 95% for polyps. Auditing barium enema performance by comparison with follow-up colonoscopy results in a sensitivity that is biased in favour of the barium enema, since, generally, patients Author for correspondence and guarantor of study: Dr. A. H. Chapman, Department of Radiology, St James's University Hospital, Leeds LS9 7TF, U.K. Fax: 0113 2836951; E-mail: AnthonyH [email protected] 0009-9260/02/$35
with a positive barium enema are the ones referred for colonoscopy and so false-negatives are ignored. This method of audit also relies on colonoscopy being a satisfactory gold standard. This study seeks to compare the sensitivities of radiographer- and radiologist-performed barium enemas for the detection of colorectal cancer (CRC). The method chosen was a retrospective pathological case review, an approach recommended by the Royal College of Radiologists in their guidelines on clinical governance [3]. The guidelines recommend the use of data from the cancer registry, a source that was unavailable when this study began. However, as cases of CRC throughout the city of Leeds are dealt with by a single acute Trust it was possible to obtain the required information from the Trust's Department of Histopathology.
MATERIALS AND METHODS
In this retrospective study computerized records in the Department of Histopathology were interrogated to # 2002 The Royal College of Radiologists
SENSITIVITY COMPARISON OF RADIOGRAPHER VS RADIOLOGIST PERFORMED DOUBLE CONTRAST BARIUM ENEMA
605
produce a list of all patients with a positive diagnosis of CRC in the 3-years before 1999. The departmental database was searched using codes for `colon' and/or `rectum' and morphology codes for `adenocarcinoma', `carcinoma' or `neoplasm'. A total of 478 cases were identi®ed by this method. Further analysis was undertaken of cases positive for CRC, where multiple biopsies had been taken and where there were multiple topographies and morphologies within the same entry. A radiological management system allowed radiological investigations of each patient to be tracked to determine the radiological investigations that had been performed over a period of 3 years before the time of histological diagnosis. These were further sorted to determine the cases that had DCBE performed before endoscopy or other abdominal imaging investigations that had made a diagnosis of CRC. After 1999, a similar audit was performed regularly each month for 2 years to see if any further cases of CRC, where barium enemas had been performed, came to the pathology department. During this period radiographer-performed examinations were undertaken by 11 radiographers with varying degrees of experience, ranging from 4 years to newly trained. The radiologist-performed examinations were undertaken by 14 radiologists: ®ve consultants and nine trainees at various stages in their training. The radiographers produced a written report after completing each examination. This report was made available to the radiologist who provided the de®nitive report. With the exception of in-patient examinations, the radiologist batch reported the radiographer's studies at a time after the patient had left the department.
false-negative in 16 (9.1%), and one case was abandoned because of faecal loading (0.6%). There were 24 histologically proven cancers where the barium enema failed to make the diagnosis. Eight were in the caecum or ascending colon, one was in the distal transverse colon, one in the splenic ¯exure, and 14 were recto-sigmoid. There were two cases with equivocal ®ndings. In one radiologist-performed study, a ®lling defect in the distal sigmoid could not be distinguished from faecal residue and so sigmoidoscopy was recommended. The ®lling defect proved to be an adenocarcinoma. In one radiographerperformed study, an area on the lateral rectal wall was thought to represent either a mucosal fold or a polyp. Subsequent endoscopy and surgical resection showed the lesion to be an adenocarcinoma. In neither case did the equivocal DCBE result in a signi®cant delay in diagnosis (histology results were available within 3 months). In one radiologist-performed study, the examination was abandoned because of faecal loading, but there was a delay of 8 months before further investigation was undertaken, when adenocarcinoma was found in the mid-sigmoid colon on ¯exible sigmoidoscopy. One radiographer-performed study was abandoned because of incontinence of barium. The barium had only reached the splenic ¯exure and so computed tomography (CT) was suggested and performed a week later revealing a tumour in the distal transverse colon. There were 20 false-negatives (8.37%). Four of these examinations had been performed by radiographers and 16 by radiologists (Table 2). Delays in diagnosis as a result of false negative reports ranged from 1 week to 31 months (mean 9.7 months).
RESULTS
DISCUSSION
In the 3-year period, 239 of 478 (50%) cases with histologically proven CRC had a DCBE as the initial investigation (Table 1). Sixty-four (26.8%) were performed by radiographers. A correct diagnosis was made in 58 (sensitivity 90.6%), the report was equivocal in one (1.6%), there were four (6.3%) false-negative reports and one case was abandoned because of patient incontinence (1.6%). One hundred and seventy-®ve (73.2%) were performed by radiologists, with a correct diagnosis in 157 (sensitivity 89.7%), the report was equivocal in one case (0.6%),
This study has found the sensitivity of the DCBE for detecting colorectal cancer to be 90% with no signi®cant dierence between radiographer- and radiologist-performed studies (90.6% and 89.7% respectively, odds ratio 1.5 which is not signi®cant, 95% con®dence interval 0.48±4.67). The sensitivities recorded in this study compare favourably with recently published studies of radiologist-performed examinations in the U.K. [4] and U.S.A. [5], which quote sensitivities of 85% and 82.5% respectively. The results of this study support the continued practice of radiographer-performed DCBEs.
Table 1 ± Cases with histologically proven CRC having barium enema as the initial examination DCBE performed by
No. of cases
Correct
Sensitivity (%)
False-negative (%)
Equivocal (%)
Abandoned/incomplete (%)
Radiographers Radiologists Total
64 175 239
58 157 215
90.6 89.7 90.0
4 (6.3) 16 (9.6) 20 (8.4)
1 (1.6) 1 (0.6) 2 (0.8)
1 (1.6) 1 (0.6) 2 (0.8)
606
CLINICAL RADIOLOGY
Table 2 ± Details of the false-negative examinations Case
Skill mix
Report
Reduced exclusion
1
R
Filling defect
2 3 4
R R R
Normal Normal Normal
5
R
Filling defect
6
R
Filling defect
7
R
Filling defect
8 9 10
R R R
Normal Filling defect Normal
11
R
Normal
12
R
Filling defect
Tortuous colon
13
R
Filling defect
14
R
Normal
Incontinence, faecal residue Tortuous colon
15
R
16
R
Extrinsic narrowing Normal
Tortuous colon
17
SM
Normal
Pronounced DD
18
SM
Normal
19
SM
Normal
20
SM
Normal
Tortuous colon
Faecal residue
Immobility/ incontinence
Faecal residue
Other pathology noted
Follow up recommended
Site of lesion
Prominent ileocaecal valve Uterine ®broid
CT
Caecum
17
Caecum Caecum Ascending colon
27 31 14
Old healed distal UC Diverticular Sigmoidoscopy disease Thickened rectal fold Diverticular disease CMH Lipoma CT Diverticular disease Rectal scar from previous adenoma removal Diverticular disease Right-sided diverticular disease Diverticular disease Diverticulitis CT Diverticular disease Diverticular disease Diverticular disease Diverticular disease
Delay (months)
Sigmoid
3
Sigmoid
1
Sigmoid
2
Caecum Splenic ¯exure Sigmoid
13 1 27
Caecum
27
Sigmoid
8
Ascending colon
2
Recto-sigmoid
1
Sigmoid
2
Recto-sigmoid
1
Sigmoid
1
Rectum
7
Rectum
6
Sigmoid
3
Rradiologist performed examination; SMradiographer performed examination; CTcomputed tomography; UCulcerative colitis; DDdiverticular disease; CMHcircular muscle hypertrophy.
Speci®city cannot be calculated from this study as the number of true-negatives and false-positives is unknown. Similarly, it is not possible to determine from this study whether similar results would be obtained for diagnosing adenomatous polyps, an important consideration if the barium enema is to have a role in any future CRC screening programme. Although most radiologist-performed studies were single reported, the radiographer-performed DCBEs were double reported, with radiographers producing written comments for each examination which were then made available to the radiologist reporting the study. Double reporting of DCBEs by two radiologists is known to reduce errors of perception [6] and, as radiographers become experienced in reporting their examinations, a reduction in perception errors is to be expected. Our radiographers had varying degrees of experience of reporting DCBEs but even so this double reporting may have biased the results in favour of the radiographer-performed examinations. The reporting of radiographer-performed studies tends to fall to a small number of radiologists in a department who
have a speci®c interest in gastrointestinal radiology. This specialization in DCBE reporting is likely to have improved radiologists' reporting skills. Many studies that have determined DCBE sensitivity by using colonoscopy as a gold standard have been biased in favour of the DCBE, as colonoscopy has been con®ned to those with a positive DCBE and so false-negative examinations have been excluded [7]. Selecting all cases with histological proof of CRC and then determining if a DCBE has been performed and whether or not the study diagnosed the CRC means that false-negative examinations are included. Even this method is not free from bias [7]; if cases are included that are referred just before the time of reviewing the pathology database, then there will be bias favouring the DCBE. This is because carcinomas missed at the time of DCBE will not be included in the study results as they will re-present clinically after the study has been completed. This study looked back 3 years before the time of reviewing the pathology database and so may be biased in favour of the barium enema. To minimize this bias, after completion of
SENSITIVITY COMPARISON OF RADIOGRAPHER VS RADIOLOGIST PERFORMED DOUBLE CONTRAST BARIUM ENEMA
the audit, we allowed a period of 2 years for such cases to come to light. Alternatively, if the study extends too many years before the time of reviewing the pathology database, the study will include barium enemas performed before the cancer has developed and such cases will be classi®ed as false-negatives, giving results that are biased against the barium enema. Such biases must be kept in mind when comparing results with other studies. We interrogated our own computerized pathology department database rather than the cancer registry since this second option was not available at the start of the study. The cancer registry might have identi®ed a small number of extra cases referred to other hospitals following their barium enema examination but this should not invalidate our conclusions. Following the initial audit we have followed the Royal College of Radiologists guidelines on clinical governance [3] relating to barium enema examinations and review our cases on a regular monthly basis. In time our database will extend over a longer period and it will be possible to determine with even greater precision the sensitivity of the barium enema for diagnosing CRC. However, a comparison between radiologist- and radiographer-performed studies may then not be possible as barium enema workload continues to transfer to radiographers. This continuing audit involves a regular (monthly) update of pathologically con®rmed cases of CRC being identi®ed to the radiology department by the pathology department. These data are then entered onto a standard database which is compared with the radiology information system (RIS) to determine whether a DCBE was used to make the diagnosis. For any interested department that
607
would like to implement audit along similar lines, a sample blank database (Microsoft Access format) is available for download from our website (www.bariumenema.co.uk). Our hope is that other radiology departments will choose to audit barium enemas in a similar way so that results can be compared and standards developed. Acknowledgements. Our thanks to Dr N. Scott, Consultant Pathologist, for his help in arranging a monthly search of his department's computer database. REFERENCES 1 Mannion RAJ, Bewell J, Langan C, Robertson M, Chapman AH. Barium enema training programme for radiographers: a pilot study. Clin Radiol 1995;50:715±719. 2 Law RL, Longsta AJ, Slack N. A retrospective 5-year study on the accuracy of the barium enema examination performed by radiographers. Clin Radiol 1999;54:80±84. 3 Lacey GE, Godwin R, Manhire A. Clinical Governance and Revalidation: A Practical Guide for Radiologists. London, U.K.: Royal College of Radiologists, 2000; 42±43. 4 Thomas RD, Fairhurst JJ, Frost RA. Wessex regional radiology audit: barium enema in colo-rectal carcinoma. Clin Radiol 1995;50: 647±650. 5 Rex DK, Rahami EY, Haseman JH, Lemmel GT, Kaster S, Buckley JS. Relative sensitivity of colonoscopy and barium enema for detection of colorectal cancer in clinical practice. Gastroenterology 1997;112:17±23. 6 Markus JB, Somers S, O'Malley BP, Stevenson GW. Doublecontrast barium enema studies: eect of multiple reading on perception error. Radiology 1990;1757:155±156. 7 Glick S, Wagner JL, Johnson CD. Cost-eectiveness of doublecontrast barium enema in screening for colorectal cancer. American Journal of Roentgenology 1998;170:629±636.
Double Contrast Barium Enema Sensitivity: A Comparison of Studies by Radiographers and Radiologists D . G . C U L PA N , A . J . MI TC H E L L , S . H U G H E S , M. N U T M A N , A . H . C H A P M A N Department of Radiology, St James's University Hospital, Leeds, U.K. Received: 16 July 2001
Revised: 2 November 2001
Accepted: 1 December 2001
PURPOSE: A retrospective study of histologically proven cases of colorectal cancer (CRC) was performed to assess whether the sensitivity of the radiographer-performed double contrast barium enema (DCBE) diered from that of the radiologist-performed study. MATERIALS AND METHODS: Histologically proven cases of CRC were reviewed over a 3-year period to ascertain whether: the diagnosis had been made by DCBE in the 3 years before histological diagnosis; the lesion had been correctly diagnosed; the examination had been performed by a radiologist or radiographer. RESULTS: In the 3-year period there were 478 cases with histologically proven CRC. Of these, 239 (50%) had undergone DCBE as the initial radiological investigation of the colon. Sixty-four examinations had been performed by radiographers. A correct diagnosis was made in 58 cases (90.6%), the report was equivocal in one case (1.6%), there were four false-negatives (6.25%), and one case was abandoned (1.6%). One hundred and seventy-®ve examinations were performed by radiologists. A correct diagnosis was made in 157 cases (89.7%), the report was equivocal in one case (0.6%), there were 16 false-negatives (9.1%), and one case was abandoned (0.6%). CONCLUSION: A sensitivity of 90.6% for radiographer-performed studies compared favourably with 89.7% for radiologist-performed studies and supports the practice of radiographers undertaking barium enemas. Culpan, D. G. et al. (2002). Clinical Radiology 57, 604±607. # 2002 The Royal College of Radiologists Key words: barium enema, radiographer, radiologist, sensitivity, skills mix, colorectal cancer.
The practice of radiographers performing double contrast barium enemas (DCBEs) has been increasing in the U.K. over the past 8 years, since a pilot study [1] showed that examinations performed by radiographers were comparable in technical quality to those performed by radiologists. Since then, over 600 radiographers have attended a training course (Leeds Barium Enema Course for Radiographers) which was developed following the pilot study. Supervising radiologists and radiographers performing barium enemas will wish to know that standards have been maintained following the introduction of this form of skills mix. Law et al. [2], by using colonoscopy as a gold standard, reported a sensitivity for radiographer-performed barium enemas of 95% for carcinomas and 95% for polyps. Auditing barium enema performance by comparison with follow-up colonoscopy results in a sensitivity that is biased in favour of the barium enema, since, generally, patients Author for correspondence and guarantor of study: Dr. A. H. Chapman, Department of Radiology, St James's University Hospital, Leeds LS9 7TF, U.K. Fax: 0113 2836951; E-mail: AnthonyH [email protected] 0009-9260/02/$35
with a positive barium enema are the ones referred for colonoscopy and so false-negatives are ignored. This method of audit also relies on colonoscopy being a satisfactory gold standard. This study seeks to compare the sensitivities of radiographer- and radiologist-performed barium enemas for the detection of colorectal cancer (CRC). The method chosen was a retrospective pathological case review, an approach recommended by the Royal College of Radiologists in their guidelines on clinical governance [3]. The guidelines recommend the use of data from the cancer registry, a source that was unavailable when this study began. However, as cases of CRC throughout the city of Leeds are dealt with by a single acute Trust it was possible to obtain the required information from the Trust's Department of Histopathology.
MATERIALS AND METHODS
In this retrospective study computerized records in the Department of Histopathology were interrogated to # 2002 The Royal College of Radiologists
SENSITIVITY COMPARISON OF RADIOGRAPHER VS RADIOLOGIST PERFORMED DOUBLE CONTRAST BARIUM ENEMA
605
produce a list of all patients with a positive diagnosis of CRC in the 3-years before 1999. The departmental database was searched using codes for `colon' and/or `rectum' and morphology codes for `adenocarcinoma', `carcinoma' or `neoplasm'. A total of 478 cases were identi®ed by this method. Further analysis was undertaken of cases positive for CRC, where multiple biopsies had been taken and where there were multiple topographies and morphologies within the same entry. A radiological management system allowed radiological investigations of each patient to be tracked to determine the radiological investigations that had been performed over a period of 3 years before the time of histological diagnosis. These were further sorted to determine the cases that had DCBE performed before endoscopy or other abdominal imaging investigations that had made a diagnosis of CRC. After 1999, a similar audit was performed regularly each month for 2 years to see if any further cases of CRC, where barium enemas had been performed, came to the pathology department. During this period radiographer-performed examinations were undertaken by 11 radiographers with varying degrees of experience, ranging from 4 years to newly trained. The radiologist-performed examinations were undertaken by 14 radiologists: ®ve consultants and nine trainees at various stages in their training. The radiographers produced a written report after completing each examination. This report was made available to the radiologist who provided the de®nitive report. With the exception of in-patient examinations, the radiologist batch reported the radiographer's studies at a time after the patient had left the department.
false-negative in 16 (9.1%), and one case was abandoned because of faecal loading (0.6%). There were 24 histologically proven cancers where the barium enema failed to make the diagnosis. Eight were in the caecum or ascending colon, one was in the distal transverse colon, one in the splenic ¯exure, and 14 were recto-sigmoid. There were two cases with equivocal ®ndings. In one radiologist-performed study, a ®lling defect in the distal sigmoid could not be distinguished from faecal residue and so sigmoidoscopy was recommended. The ®lling defect proved to be an adenocarcinoma. In one radiographerperformed study, an area on the lateral rectal wall was thought to represent either a mucosal fold or a polyp. Subsequent endoscopy and surgical resection showed the lesion to be an adenocarcinoma. In neither case did the equivocal DCBE result in a signi®cant delay in diagnosis (histology results were available within 3 months). In one radiologist-performed study, the examination was abandoned because of faecal loading, but there was a delay of 8 months before further investigation was undertaken, when adenocarcinoma was found in the mid-sigmoid colon on ¯exible sigmoidoscopy. One radiographer-performed study was abandoned because of incontinence of barium. The barium had only reached the splenic ¯exure and so computed tomography (CT) was suggested and performed a week later revealing a tumour in the distal transverse colon. There were 20 false-negatives (8.37%). Four of these examinations had been performed by radiographers and 16 by radiologists (Table 2). Delays in diagnosis as a result of false negative reports ranged from 1 week to 31 months (mean 9.7 months).
RESULTS
DISCUSSION
In the 3-year period, 239 of 478 (50%) cases with histologically proven CRC had a DCBE as the initial investigation (Table 1). Sixty-four (26.8%) were performed by radiographers. A correct diagnosis was made in 58 (sensitivity 90.6%), the report was equivocal in one (1.6%), there were four (6.3%) false-negative reports and one case was abandoned because of patient incontinence (1.6%). One hundred and seventy-®ve (73.2%) were performed by radiologists, with a correct diagnosis in 157 (sensitivity 89.7%), the report was equivocal in one case (0.6%),
This study has found the sensitivity of the DCBE for detecting colorectal cancer to be 90% with no signi®cant dierence between radiographer- and radiologist-performed studies (90.6% and 89.7% respectively, odds ratio 1.5 which is not signi®cant, 95% con®dence interval 0.48±4.67). The sensitivities recorded in this study compare favourably with recently published studies of radiologist-performed examinations in the U.K. [4] and U.S.A. [5], which quote sensitivities of 85% and 82.5% respectively. The results of this study support the continued practice of radiographer-performed DCBEs.
Table 1 ± Cases with histologically proven CRC having barium enema as the initial examination DCBE performed by
No. of cases
Correct
Sensitivity (%)
False-negative (%)
Equivocal (%)
Abandoned/incomplete (%)
Radiographers Radiologists Total
64 175 239
58 157 215
90.6 89.7 90.0
4 (6.3) 16 (9.6) 20 (8.4)
1 (1.6) 1 (0.6) 2 (0.8)
1 (1.6) 1 (0.6) 2 (0.8)
606
CLINICAL RADIOLOGY
Table 2 ± Details of the false-negative examinations Case
Skill mix
Report
Reduced exclusion
1
R
Filling defect
2 3 4
R R R
Normal Normal Normal
5
R
Filling defect
6
R
Filling defect
7
R
Filling defect
8 9 10
R R R
Normal Filling defect Normal
11
R
Normal
12
R
Filling defect
Tortuous colon
13
R
Filling defect
14
R
Normal
Incontinence, faecal residue Tortuous colon
15
R
16
R
Extrinsic narrowing Normal
Tortuous colon
17
SM
Normal
Pronounced DD
18
SM
Normal
19
SM
Normal
20
SM
Normal
Tortuous colon
Faecal residue
Immobility/ incontinence
Faecal residue
Other pathology noted
Follow up recommended
Site of lesion
Prominent ileocaecal valve Uterine ®broid
CT
Caecum
17
Caecum Caecum Ascending colon
27 31 14
Old healed distal UC Diverticular Sigmoidoscopy disease Thickened rectal fold Diverticular disease CMH Lipoma CT Diverticular disease Rectal scar from previous adenoma removal Diverticular disease Right-sided diverticular disease Diverticular disease Diverticulitis CT Diverticular disease Diverticular disease Diverticular disease Diverticular disease
Delay (months)
Sigmoid
3
Sigmoid
1
Sigmoid
2
Caecum Splenic ¯exure Sigmoid
13 1 27
Caecum
27
Sigmoid
8
Ascending colon
2
Recto-sigmoid
1
Sigmoid
2
Recto-sigmoid
1
Sigmoid
1
Rectum
7
Rectum
6
Sigmoid
3
Rradiologist performed examination; SMradiographer performed examination; CTcomputed tomography; UCulcerative colitis; DDdiverticular disease; CMHcircular muscle hypertrophy.
Speci®city cannot be calculated from this study as the number of true-negatives and false-positives is unknown. Similarly, it is not possible to determine from this study whether similar results would be obtained for diagnosing adenomatous polyps, an important consideration if the barium enema is to have a role in any future CRC screening programme. Although most radiologist-performed studies were single reported, the radiographer-performed DCBEs were double reported, with radiographers producing written comments for each examination which were then made available to the radiologist reporting the study. Double reporting of DCBEs by two radiologists is known to reduce errors of perception [6] and, as radiographers become experienced in reporting their examinations, a reduction in perception errors is to be expected. Our radiographers had varying degrees of experience of reporting DCBEs but even so this double reporting may have biased the results in favour of the radiographer-performed examinations. The reporting of radiographer-performed studies tends to fall to a small number of radiologists in a department who
have a speci®c interest in gastrointestinal radiology. This specialization in DCBE reporting is likely to have improved radiologists' reporting skills. Many studies that have determined DCBE sensitivity by using colonoscopy as a gold standard have been biased in favour of the DCBE, as colonoscopy has been con®ned to those with a positive DCBE and so false-negative examinations have been excluded [7]. Selecting all cases with histological proof of CRC and then determining if a DCBE has been performed and whether or not the study diagnosed the CRC means that false-negative examinations are included. Even this method is not free from bias [7]; if cases are included that are referred just before the time of reviewing the pathology database, then there will be bias favouring the DCBE. This is because carcinomas missed at the time of DCBE will not be included in the study results as they will re-present clinically after the study has been completed. This study looked back 3 years before the time of reviewing the pathology database and so may be biased in favour of the barium enema. To minimize this bias, after completion of
SENSITIVITY COMPARISON OF RADIOGRAPHER VS RADIOLOGIST PERFORMED DOUBLE CONTRAST BARIUM ENEMA
the audit, we allowed a period of 2 years for such cases to come to light. Alternatively, if the study extends too many years before the time of reviewing the pathology database, the study will include barium enemas performed before the cancer has developed and such cases will be classi®ed as false-negatives, giving results that are biased against the barium enema. Such biases must be kept in mind when comparing results with other studies. We interrogated our own computerized pathology department database rather than the cancer registry since this second option was not available at the start of the study. The cancer registry might have identi®ed a small number of extra cases referred to other hospitals following their barium enema examination but this should not invalidate our conclusions. Following the initial audit we have followed the Royal College of Radiologists guidelines on clinical governance [3] relating to barium enema examinations and review our cases on a regular monthly basis. In time our database will extend over a longer period and it will be possible to determine with even greater precision the sensitivity of the barium enema for diagnosing CRC. However, a comparison between radiologist- and radiographer-performed studies may then not be possible as barium enema workload continues to transfer to radiographers. This continuing audit involves a regular (monthly) update of pathologically con®rmed cases of CRC being identi®ed to the radiology department by the pathology department. These data are then entered onto a standard database which is compared with the radiology information system (RIS) to determine whether a DCBE was used to make the diagnosis. For any interested department that
607
would like to implement audit along similar lines, a sample blank database (Microsoft Access format) is available for download from our website (www.bariumenema.co.uk). Our hope is that other radiology departments will choose to audit barium enemas in a similar way so that results can be compared and standards developed. Acknowledgements. Our thanks to Dr N. Scott, Consultant Pathologist, for his help in arranging a monthly search of his department's computer database. REFERENCES 1 Mannion RAJ, Bewell J, Langan C, Robertson M, Chapman AH. Barium enema training programme for radiographers: a pilot study. Clin Radiol 1995;50:715±719. 2 Law RL, Longsta AJ, Slack N. A retrospective 5-year study on the accuracy of the barium enema examination performed by radiographers. Clin Radiol 1999;54:80±84. 3 Lacey GE, Godwin R, Manhire A. Clinical Governance and Revalidation: A Practical Guide for Radiologists. London, U.K.: Royal College of Radiologists, 2000; 42±43. 4 Thomas RD, Fairhurst JJ, Frost RA. Wessex regional radiology audit: barium enema in colo-rectal carcinoma. Clin Radiol 1995;50: 647±650. 5 Rex DK, Rahami EY, Haseman JH, Lemmel GT, Kaster S, Buckley JS. Relative sensitivity of colonoscopy and barium enema for detection of colorectal cancer in clinical practice. Gastroenterology 1997;112:17±23. 6 Markus JB, Somers S, O'Malley BP, Stevenson GW. Doublecontrast barium enema studies: eect of multiple reading on perception error. Radiology 1990;1757:155±156. 7 Glick S, Wagner JL, Johnson CD. Cost-eectiveness of doublecontrast barium enema in screening for colorectal cancer. American Journal of Roentgenology 1998;170:629±636.