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Hemoccult test in screening for colorectal cancers
806
CORRESPONDENCE
9. Matsukawa A, Hoshi K, Kaise A. Sasaki I, Hashimoto Y, Amaha K. The cardiovascular effect of famotidine in intensive care patients. J Intensive Care Med 1986;10:763-767. 10. Omote K, Namiki A, Sumita S, Takahashi T, Ujike Y, Hagiwara T. Comparative studies on hemodynamic effects of intravenous cimetidine, ranitidine, and famotidine in intensive care patients. Jap J Anesth 1987;36:940-947. 11. Ohnishi K, Saito M, Nomura F, Okuda K, Suzuki N, Ohtsuki T, Goto N. Takashi M. Effect of famotidine on hepatic hemodynamits and peptic ulcer. Am J Gastroenterology 1987;82:415-418. 12. Salmon P. Darragh A, Fitzgerald D. Lambe R, Kenny M, Hirata Y. Lack of effect of famotidine on cardiac performance assessed by non-invasive hemodynamic measurements. Eur J Clin Pharmacol1989;(Suppl):A136.
Hemoccult Test in Screening for Colorectal Cancers Dear Sir: The paper by Mandel et al. (#l) reported on the sensitivity, specificity, and positive predictivity of the hemoccult test in screening for colorectal cancers. The results were as follows: sensitivity, 89.3%; specificity, 92.7%; and positive predictivity, 5.6%. The false-positive rate of 7.3% is the proportion of individuals who had a positive hemoccult test and were free of colorectal cancer. As the authors indicate, most of the “false-positives” had another lesion that could explain their bleeding such as polyps, hemorrhoids, or diverticulitis. Hemoccult testing is inappropriate for screening for hemorrhoids or diverticular disease, but may be appropriate for screening for polyps as well as for cancer. I suspect that many readers would like to know the combined rate of detection of cancers plus polyps and the false-positive rate and the positive predictive value of the test using this criterion. JOHN W. D. MCDONALD, M.D.
Department of Medicine University Hospital London, Ontario N6A 5A.5 Reply. Dr. McDonald raises a pertinent point regarding hemoccult testing for colorectal cancers. We intend to address this in a later paper, but perhaps a brief comment is warranted in view of the interest. Preliminary results indicate that among the subjects with a positive slide set [at least 1 positive slide out of a set of 6), 19.4% were found to have a neoplastic polyp following colonoscopy. An additional 2.5% were diagnosed with colorectal cancer. Thus, the positive predictivity for cancer and neoplastic polyps is 21.9%. JACK8 MANDEL, PH.D.,M.P.H. School of Public Health University of Minnesota Minneapolis, Minnesota 55455
Gallstone Shock-Wave Therapy Dear Sir: We have read with great interest the article by Ponchon et al. (11, using extracorporeal shock-wave lithotripsy and bile salt therapy in the management of symptomatic patients with gallstones disease. However this study raises a number of important questions. (a] This group has included 135 (25%) patients from a pool of 531 referred to their center for gallstone lithotripsy. They have not documented the reasons for the 25% patient inclusion. This figure is small considering the 28% suitability rate reported by Sackmann et al. employing much stricter selection criteria (2). In our experience where the selection criteria were extended to include all patients who had functioning gallbladders and had radiolucent stones of any
GASTROENTEROLOGY
Vol. 98, No. 3
size and number, and also radio-opaque stones <30 mm in diameter, we included up to 60% of our gallstone population (3). (b) They report that 45 of the 135 patients studied refused retreatment following 1 or 2 lithotripsy sessions. This is not surprising since all the treatments were performed with either an epidural anesthetic or iv. sedation and required a median hospital stay of 2 days per treatment. We feel that when treating patients with a larger stone load, as reported in this study, retreatment becomes necessary and all treatments can be performed without sedation or anesthesia as an outpatient procedure using a piezoelectric lithotripter (EDAP LT-01) (3). (c) Two different lithotripters have been used in their treatments. It seems that the first lithotripter had a smaller semiellipsoid and was a more powerful machine than the second, requiring fewer shocks. However, there has been no reference in their results to the efficacy of fragmentation using the two different machines. (d) They report the stone-free rate only in patients who have achieved partial or successful gallstone fragmentation (Table 4), and did not include patients who had no fragmentation. This makes their data incomparable with other groups (21. In addition, this method of calculation makes their stone-free rate speciously high. [e) In the results section the authors refer to the “results of oral bile acid dissolution” and “complication during oral bile salt dissolution.” Is there a reason for this inconsistency? Regarding these comments, we feel the results of Ponchon et al. have to be interpreted with caution. F.B.V.KEANE, M.D., FRCSI Department of Surgery Meath Hospital Dublin 8. Ireland 1. Ponchon T. Barkun A, Pujol B. Mestas JL, Lambert R. Gallstone disappearance after extracorporeal lithotripsy and oral bile acid therapy. Gastroenterology 1989;97:457-463. 2. Sackman M, Delius M, Sauerbruch T, et al. Shock Wave Lithotripsy of gallstones. The first 175 patients. New Engl J Med 1988;318:393-397. 3. Darzi A, Monson JRT, O’Morain C, Tanner WA, Keane FBV. Extension of selection criteria for extracorporeal shock wave lithotripsy for gallstones. Br Med J 1989;299:302-303. Reply. We thank Dw. Darzi and Keane for the interest with which they read our article (1). We are pleased to clarify points that are raised. Although our criteria are slightly broader than those defined by Dr. Sackmann et al. [2], we do not believe that the selection rates of both series are completely comparable as these 2 early studies were performed with a varying level of patient and physician education in regards to indications for biliary lithotripsy. Although a denominator could be determined from our registers, the referral system used in our institution did not permit a full breakdown of excluded patients according to unfulfilled selection criteria. The comparative fragmentation efficacies of different lithotripter systems remains unclear as do their respective optimal treatment protocols. We therefore believe that any discussion or conclusions on patient acceptability when contrasting electrohydraulic and piezoelectric or electromagnetic systems at this time are premature. We treated 29 patients with an initial lithotripter, and 115 with a second generation machine achieving satisfactory fragmentations of 65% and 45%. respectively. We analyzed the outcome of remaining fragments after lithotripsy and our results were stratified according to the outcome of fragmentation postlithotripsy rather than initial stone characteristics. As we did not administer bile salts to the patients in whom no fragmentation had occurred (24% of all patients), they were not included in our stone-free rate follow-up results. We believe that this is clearly
CORRESPONDENCE
9. Matsukawa A, Hoshi K, Kaise A. Sasaki I, Hashimoto Y, Amaha K. The cardiovascular effect of famotidine in intensive care patients. J Intensive Care Med 1986;10:763-767. 10. Omote K, Namiki A, Sumita S, Takahashi T, Ujike Y, Hagiwara T. Comparative studies on hemodynamic effects of intravenous cimetidine, ranitidine, and famotidine in intensive care patients. Jap J Anesth 1987;36:940-947. 11. Ohnishi K, Saito M, Nomura F, Okuda K, Suzuki N, Ohtsuki T, Goto N. Takashi M. Effect of famotidine on hepatic hemodynamits and peptic ulcer. Am J Gastroenterology 1987;82:415-418. 12. Salmon P. Darragh A, Fitzgerald D. Lambe R, Kenny M, Hirata Y. Lack of effect of famotidine on cardiac performance assessed by non-invasive hemodynamic measurements. Eur J Clin Pharmacol1989;(Suppl):A136.
Hemoccult Test in Screening for Colorectal Cancers Dear Sir: The paper by Mandel et al. (#l) reported on the sensitivity, specificity, and positive predictivity of the hemoccult test in screening for colorectal cancers. The results were as follows: sensitivity, 89.3%; specificity, 92.7%; and positive predictivity, 5.6%. The false-positive rate of 7.3% is the proportion of individuals who had a positive hemoccult test and were free of colorectal cancer. As the authors indicate, most of the “false-positives” had another lesion that could explain their bleeding such as polyps, hemorrhoids, or diverticulitis. Hemoccult testing is inappropriate for screening for hemorrhoids or diverticular disease, but may be appropriate for screening for polyps as well as for cancer. I suspect that many readers would like to know the combined rate of detection of cancers plus polyps and the false-positive rate and the positive predictive value of the test using this criterion. JOHN W. D. MCDONALD, M.D.
Department of Medicine University Hospital London, Ontario N6A 5A.5 Reply. Dr. McDonald raises a pertinent point regarding hemoccult testing for colorectal cancers. We intend to address this in a later paper, but perhaps a brief comment is warranted in view of the interest. Preliminary results indicate that among the subjects with a positive slide set [at least 1 positive slide out of a set of 6), 19.4% were found to have a neoplastic polyp following colonoscopy. An additional 2.5% were diagnosed with colorectal cancer. Thus, the positive predictivity for cancer and neoplastic polyps is 21.9%. JACK8 MANDEL, PH.D.,M.P.H. School of Public Health University of Minnesota Minneapolis, Minnesota 55455
Gallstone Shock-Wave Therapy Dear Sir: We have read with great interest the article by Ponchon et al. (11, using extracorporeal shock-wave lithotripsy and bile salt therapy in the management of symptomatic patients with gallstones disease. However this study raises a number of important questions. (a] This group has included 135 (25%) patients from a pool of 531 referred to their center for gallstone lithotripsy. They have not documented the reasons for the 25% patient inclusion. This figure is small considering the 28% suitability rate reported by Sackmann et al. employing much stricter selection criteria (2). In our experience where the selection criteria were extended to include all patients who had functioning gallbladders and had radiolucent stones of any
GASTROENTEROLOGY
Vol. 98, No. 3
size and number, and also radio-opaque stones <30 mm in diameter, we included up to 60% of our gallstone population (3). (b) They report that 45 of the 135 patients studied refused retreatment following 1 or 2 lithotripsy sessions. This is not surprising since all the treatments were performed with either an epidural anesthetic or iv. sedation and required a median hospital stay of 2 days per treatment. We feel that when treating patients with a larger stone load, as reported in this study, retreatment becomes necessary and all treatments can be performed without sedation or anesthesia as an outpatient procedure using a piezoelectric lithotripter (EDAP LT-01) (3). (c) Two different lithotripters have been used in their treatments. It seems that the first lithotripter had a smaller semiellipsoid and was a more powerful machine than the second, requiring fewer shocks. However, there has been no reference in their results to the efficacy of fragmentation using the two different machines. (d) They report the stone-free rate only in patients who have achieved partial or successful gallstone fragmentation (Table 4), and did not include patients who had no fragmentation. This makes their data incomparable with other groups (21. In addition, this method of calculation makes their stone-free rate speciously high. [e) In the results section the authors refer to the “results of oral bile acid dissolution” and “complication during oral bile salt dissolution.” Is there a reason for this inconsistency? Regarding these comments, we feel the results of Ponchon et al. have to be interpreted with caution. F.B.V.KEANE, M.D., FRCSI Department of Surgery Meath Hospital Dublin 8. Ireland 1. Ponchon T. Barkun A, Pujol B. Mestas JL, Lambert R. Gallstone disappearance after extracorporeal lithotripsy and oral bile acid therapy. Gastroenterology 1989;97:457-463. 2. Sackman M, Delius M, Sauerbruch T, et al. Shock Wave Lithotripsy of gallstones. The first 175 patients. New Engl J Med 1988;318:393-397. 3. Darzi A, Monson JRT, O’Morain C, Tanner WA, Keane FBV. Extension of selection criteria for extracorporeal shock wave lithotripsy for gallstones. Br Med J 1989;299:302-303. Reply. We thank Dw. Darzi and Keane for the interest with which they read our article (1). We are pleased to clarify points that are raised. Although our criteria are slightly broader than those defined by Dr. Sackmann et al. [2], we do not believe that the selection rates of both series are completely comparable as these 2 early studies were performed with a varying level of patient and physician education in regards to indications for biliary lithotripsy. Although a denominator could be determined from our registers, the referral system used in our institution did not permit a full breakdown of excluded patients according to unfulfilled selection criteria. The comparative fragmentation efficacies of different lithotripter systems remains unclear as do their respective optimal treatment protocols. We therefore believe that any discussion or conclusions on patient acceptability when contrasting electrohydraulic and piezoelectric or electromagnetic systems at this time are premature. We treated 29 patients with an initial lithotripter, and 115 with a second generation machine achieving satisfactory fragmentations of 65% and 45%. respectively. We analyzed the outcome of remaining fragments after lithotripsy and our results were stratified according to the outcome of fragmentation postlithotripsy rather than initial stone characteristics. As we did not administer bile salts to the patients in whom no fragmentation had occurred (24% of all patients), they were not included in our stone-free rate follow-up results. We believe that this is clearly