- Email: [email protected]
Appendicectomy
in front collisions. In rear-end car collisions, as in our study, use or non-use of seat belts could hardly influence the neck hyperextension force. de Mol and Heijer state that we do not define whiplash disorders. Although no generally accepted definition of the late-whiplash syndrome exists, chronic neck pain and headache are the symptoms most frequently mentioned in published work, and usually presented as the most annoying complaints by patients with chronic disability after whiplash. Consequently, the Quebec Task Force on WAD lists neck complaints and headache at the top of their tables for the clinical spectrum of WAD and on prevalence of symptoms at follow-up.2 A definition of trauma-induced disability was unnecessary since none of the 202 subjects stated that they had persistent or chronic symptoms due to the accident. We agree that a very large sample of accidents would have been needed if the main aim of our study had been to disprove the existence of the late-whiplash syndrome. However, we restricted our study to estimate occurrences in the suggested range of 12–75% of patients reported to have persistent symptoms after an injury to the neck. Our sample size and the design of our study (blinded; self-controlled, and matched-controlled) was adequate to estimate occurrences in this range. We concluded that the prevalence of late-whiplash syndrome seems to be less common than these published estimates. Freeman and Croft suppose that our intention was (or should have been?) to determine the rate of progression from confirmed acute symptoms to the late-whiplash syndrome; this is incorrect. With our study design we could only identify persons who remembered acute post-traumatic complaints 1–3 years after the accident. Furthermore, our intention was to study the evolution and prevalence of chronic symptoms in an unselected cohort at risk. To achieve this, exposure to a substantial rear-end car collision was a necessary and sufficient inclusion criterion. They also state that our study suffers from inaccurate interpretation of published work. In fact, we compared the prevalence of chronic neck pain in Norway with reported rates of chronic neck pain in the latewhiplash syndrome. The rates cited by Freeman and Croft refer to any neck pain, in part together with other symptoms. These rates are of the same magnitude as the prevalence of 34·4% of any neck pain found in the general Norwegian population.3,4 *Harald Schrader, Gunnar Bovim, Trond Sand *Department of Neurology, Trondheim University Hospital, 7006 Trondheim, Norway
1 2
3 4
Galasko CSB, Murray PM, Pitcher M, et al. Neck sprains after road traffic accidents. Injury 1993; 24: 155–57. Scientific Monograph of the Quebec Task Force on Whiplash Associated Disorders: Redefining “whiplash” and its management. Cassidy (ed, coord). Spine 1995; 20: 8/S. Bovim G, Schrader H, Sand T. Neck pain in the general population. Spine 1994; 19: 1307–09. Croft AC. Neck pain in the general population. Spine 1995; 20: 6–29.
Thermal cycler from recycled printer SIR—The capital outlay required for a thermal cycler for PCR may be an obstacle to researchers with limited resources, especially those in developing countries. Most machines operate on the semiconductor Peltier principle1 but a robotic thermal cycler can easily be made from a scrapped wide-bed printer connected to a personal computer.
126
Heating block
Printer
Figure: Thermal cycler from recycled printer
The carriage and paper-feed mechanisms are adapted to move the PCR reaction tubes between three laboratory heating blocks set at appropriate temperatures. After removing the printhead, a rocking arm is mounted on the printer carriage, and it is raised and lowered by the winding drum which slides on the paper tractor shaft (figure). I made the rocking arm from “Meccano” with a simple parallel linkage to ensure an approximately vertical movement of tubes. BASIC programmes, irrespective of type or cost of the computer or printer used, invariably possess appropriate printer-control commands. I will supply a printout of an MS-DOS QBASIC programme to interested readers on request. John Frean Department of Medical Microbiology, School of Pathology of the SA Institute for Medical Research and University of the Witwatersrand, PO Box 1038, Johannesburg 2000, South Africa
1
Oste O. PCR automation. In: Erlich HA, ed. PCR technology: principles and applications for DNA amplification. New York: Stockton Press, 1989: 23–30.
Appendicectomy SIR—Wang and colleagues (April 20, p 1076)1 report raised cytokine levels in 22% of histologically normal appendices from patients with acute right lower quadrant pain. Their conclusion that this is clear evidence of an inflammatory response is undoubtedly correct, but that this justifies appendicectomy should be regarded with caution. That the origin of appendicitis is obstruction followed by infection is firmly established.2 Why bacterial infection of the appendix wall in the absence of obstruction would lead to perforating appendicitis is also difficult to imagine, since bacterial infection per se does not lead to perforation of the ileum and colon. Wang and colleagues’ findings might be accounted for by a common, albeit underestimated, appendicitis-mimicking condition—namely, bacterial ileocaecitis. 3 This enteral infection, which is limited to the ileocaecal area, is caused by
Vol 348 • July 13, 1996
Yersinia enterocolitica, Campylobacter jejuni, and Salmonella enteritidis. Clinically, right lower quadrant pain is the predominant symptom, whereas diarrhoea is absent or only mild, which explains why this otherwise benign and selflimiting infection may lead to an unnecessary appendicectomy. The removed appendix may show endoappendicitis, which is limited to the (sub)mucosa, and never involves the muscularis. However, the appendix is often histologically normal. The seven normal appendices with raised cytokine levels in Wang and colleagues’ study could well have been from patients with bacterial ileocaecitis. It would be interesting to know whether a solid alternative diagnosis was obtained in those seven patients and especially if stool cultures were done for yersinia, campylobacter, and salmonella. Wang and colleagues’ findings might support earlier observations that bacterial ileocaecitis is responsible for a remarkable number of unnecessary appendicectomies.3,4 J B C M Puylaert Department of Diagnostic Radiology, Westeinde Hospital, 2512 VA The Hague, Netherlands
1
2 3
4
Wang Y, Reen DJ, Puri P. Is a histologically normal appendix following emergency appendicectomy always normal. Lancet 1996; 347: 1076–79. Wangensteen OH, Dennis C. Experimental proof of the obstructive origin of appendicitis in man. Ann Surg 1939; 110: 629–33. Puylaert JBCM, Vermeyden RJ, Van der Werf SDJ, Doornbos L, Koumans RKJ. Incidence and sonographic diagnosis of bacterial ileocaecitis masquerading as appendicitis. Lancet 1989; ii: 84–86. Van Noyen R, Selderslaghs R, Bekaert J, Wauters G, Vandepitte J. Bacterial ileocaecitis and appendicitis. Lancet 1990; 336: 518.
could add depth and explanation. Because indicators are often more amenable to precise measurement, they seem more salient when subjected to statistical testing. Explanatory power is thus sacrificed on the altar of precision, and the number of quantifiable variables is substantially reduced. Without the ability to explain, results will have few, if any, wider applications. Macnaughton’s assertion that “understanding in qualitative research is . . . more akin to the understanding gained from an art, rather than a science” is an antiquated argument. Both art and science are narrative and descriptive. In addition, just as we should not preclude the narrative and descriptive utility of quantitative data, we should not restrict research using qualitative methods to these domains. Narration and description provide ethnographers with data which, when applied to theory, become interpretation. Good studies in any specialty generally both describe and interpret results. Results from both quantitative and qualitative methods require “active participation of the reader to . . . relate findings to his own situation” to be implemented sensibly. These are interpretive processes, implicated in the application of research, not methodological features as Macnaughton implies. We enjoin Macnaughton to explore the rich scientific literature beyond medical journals before drawing her methodological conclusions. We look forward to the day when we can put this debate firmly in the past where it belongs. *D P Béhague, J A Ogden Departments of *Epidemiology and Population Science, and Public Health and Policy, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK
1
Qualitative research SIR—Macnaughton (April 20, p 1099)1 shows a common misunderstanding about the use of numbers in biomedical versus sociological inquiry. We hope to show that medics and social scientists use numbers to satisfy different theoretical and methodological needs. The use of statistics in the medical and social sciences follows distinct scientific traditions, characterised by particular methodological imperatives. By applying the conventional biomedical paradigm to questions of methodology in sociological research, Macnaughton loses sight of the statistically sound and yet diverse ways of understanding patterns. Although she outlines the three main uses of numbers, she discusses only quantitative variables. In addition to her neglect of categorical variables (numbers as labels), she draws the erroneous conclusion that unless “the distance between the points on . . . scales are equal”, we cannot “talk of scales and percentages with meaning”. When numbers are used appropriately in anthropological studies, they are not usually meant to provide the kind of certainty attached to the absolute values of biomedical research. The interest, rather, is in their relative values. Wallman and Baker,2 for example, show how a numerical index can be used qualitatively in so far as the analysis is primarily relational. Indeed, the difficulties Macnaughton outlines arise not with the inherent use of numbers, but with the interpretive truth, universality, and objectivity that statistical associations allegedly provide. Macnaughton argues that qualitative data are nonquantifiable because “the research is context specific”. Yet quantification bearing little relation to context leads researchers to consider indicators alone, thereby misinterpreting the dynamics between variables. As such, decontextualised research masks underlying variables that
Vol 348 • July 13, 1996
2
Macnaughton RJ. Numbers, scales, and qualitative research. Lancet 1996; 347: 1099–100. Wallman S, Baker M. Which resources pay for treatment? A model for estimating the informal economy of health. Soc Sci Med 1996; 42: 671–79.
Author’s reply SIR—Béhague and Ogden write as if they were disagreeing with me. But in so far as I can follow their argument they seem to be reaffirming some of the points I made. For example, I did not say that there are problems with the inherent use of numbers; my thesis is that the use of numbers in qualitative research suggests a false objectivity. Again, I entirely agree with them that decontextualised research masks underlying variables: that was one of my main points. Finally, my suggestion that understanding in qualitative research is more akin to the understanding gained from an art than from a science was not intended to “assert an antiquated argument” but merely to suggest an alternative way of looking at qualitative data—a way that I learned from the journals of my first degree studies in history and literature. Jane Macnaughton Department of General Practice, University of Glasgow, Glasgow G20 7LR, UK
SIR—Macnaughton1 raises fundamental issues about methods of clinical research but unfortunately perpetuates a serious misunderstanding. Qualitative research is conducted and reported by means of concepts—ie, verbally and without resort to numbers. It is increasingly promoted by medical journals as a way of understanding complex aspects of human behaviour, or organisations such as hospitals in situations in which quantification would be impossible or unhelpful.2 She specifically refers to studies of issues such as
127
1 2
3 4
Galasko CSB, Murray PM, Pitcher M, et al. Neck sprains after road traffic accidents. Injury 1993; 24: 155–57. Scientific Monograph of the Quebec Task Force on Whiplash Associated Disorders: Redefining “whiplash” and its management. Cassidy (ed, coord). Spine 1995; 20: 8/S. Bovim G, Schrader H, Sand T. Neck pain in the general population. Spine 1994; 19: 1307–09. Croft AC. Neck pain in the general population. Spine 1995; 20: 6–29.
Thermal cycler from recycled printer SIR—The capital outlay required for a thermal cycler for PCR may be an obstacle to researchers with limited resources, especially those in developing countries. Most machines operate on the semiconductor Peltier principle1 but a robotic thermal cycler can easily be made from a scrapped wide-bed printer connected to a personal computer.
126
Heating block
Printer
Figure: Thermal cycler from recycled printer
The carriage and paper-feed mechanisms are adapted to move the PCR reaction tubes between three laboratory heating blocks set at appropriate temperatures. After removing the printhead, a rocking arm is mounted on the printer carriage, and it is raised and lowered by the winding drum which slides on the paper tractor shaft (figure). I made the rocking arm from “Meccano” with a simple parallel linkage to ensure an approximately vertical movement of tubes. BASIC programmes, irrespective of type or cost of the computer or printer used, invariably possess appropriate printer-control commands. I will supply a printout of an MS-DOS QBASIC programme to interested readers on request. John Frean Department of Medical Microbiology, School of Pathology of the SA Institute for Medical Research and University of the Witwatersrand, PO Box 1038, Johannesburg 2000, South Africa
1
Oste O. PCR automation. In: Erlich HA, ed. PCR technology: principles and applications for DNA amplification. New York: Stockton Press, 1989: 23–30.
Appendicectomy SIR—Wang and colleagues (April 20, p 1076)1 report raised cytokine levels in 22% of histologically normal appendices from patients with acute right lower quadrant pain. Their conclusion that this is clear evidence of an inflammatory response is undoubtedly correct, but that this justifies appendicectomy should be regarded with caution. That the origin of appendicitis is obstruction followed by infection is firmly established.2 Why bacterial infection of the appendix wall in the absence of obstruction would lead to perforating appendicitis is also difficult to imagine, since bacterial infection per se does not lead to perforation of the ileum and colon. Wang and colleagues’ findings might be accounted for by a common, albeit underestimated, appendicitis-mimicking condition—namely, bacterial ileocaecitis. 3 This enteral infection, which is limited to the ileocaecal area, is caused by
Vol 348 • July 13, 1996
Yersinia enterocolitica, Campylobacter jejuni, and Salmonella enteritidis. Clinically, right lower quadrant pain is the predominant symptom, whereas diarrhoea is absent or only mild, which explains why this otherwise benign and selflimiting infection may lead to an unnecessary appendicectomy. The removed appendix may show endoappendicitis, which is limited to the (sub)mucosa, and never involves the muscularis. However, the appendix is often histologically normal. The seven normal appendices with raised cytokine levels in Wang and colleagues’ study could well have been from patients with bacterial ileocaecitis. It would be interesting to know whether a solid alternative diagnosis was obtained in those seven patients and especially if stool cultures were done for yersinia, campylobacter, and salmonella. Wang and colleagues’ findings might support earlier observations that bacterial ileocaecitis is responsible for a remarkable number of unnecessary appendicectomies.3,4 J B C M Puylaert Department of Diagnostic Radiology, Westeinde Hospital, 2512 VA The Hague, Netherlands
1
2 3
4
Wang Y, Reen DJ, Puri P. Is a histologically normal appendix following emergency appendicectomy always normal. Lancet 1996; 347: 1076–79. Wangensteen OH, Dennis C. Experimental proof of the obstructive origin of appendicitis in man. Ann Surg 1939; 110: 629–33. Puylaert JBCM, Vermeyden RJ, Van der Werf SDJ, Doornbos L, Koumans RKJ. Incidence and sonographic diagnosis of bacterial ileocaecitis masquerading as appendicitis. Lancet 1989; ii: 84–86. Van Noyen R, Selderslaghs R, Bekaert J, Wauters G, Vandepitte J. Bacterial ileocaecitis and appendicitis. Lancet 1990; 336: 518.
could add depth and explanation. Because indicators are often more amenable to precise measurement, they seem more salient when subjected to statistical testing. Explanatory power is thus sacrificed on the altar of precision, and the number of quantifiable variables is substantially reduced. Without the ability to explain, results will have few, if any, wider applications. Macnaughton’s assertion that “understanding in qualitative research is . . . more akin to the understanding gained from an art, rather than a science” is an antiquated argument. Both art and science are narrative and descriptive. In addition, just as we should not preclude the narrative and descriptive utility of quantitative data, we should not restrict research using qualitative methods to these domains. Narration and description provide ethnographers with data which, when applied to theory, become interpretation. Good studies in any specialty generally both describe and interpret results. Results from both quantitative and qualitative methods require “active participation of the reader to . . . relate findings to his own situation” to be implemented sensibly. These are interpretive processes, implicated in the application of research, not methodological features as Macnaughton implies. We enjoin Macnaughton to explore the rich scientific literature beyond medical journals before drawing her methodological conclusions. We look forward to the day when we can put this debate firmly in the past where it belongs. *D P Béhague, J A Ogden Departments of *Epidemiology and Population Science, and Public Health and Policy, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK
1
Qualitative research SIR—Macnaughton (April 20, p 1099)1 shows a common misunderstanding about the use of numbers in biomedical versus sociological inquiry. We hope to show that medics and social scientists use numbers to satisfy different theoretical and methodological needs. The use of statistics in the medical and social sciences follows distinct scientific traditions, characterised by particular methodological imperatives. By applying the conventional biomedical paradigm to questions of methodology in sociological research, Macnaughton loses sight of the statistically sound and yet diverse ways of understanding patterns. Although she outlines the three main uses of numbers, she discusses only quantitative variables. In addition to her neglect of categorical variables (numbers as labels), she draws the erroneous conclusion that unless “the distance between the points on . . . scales are equal”, we cannot “talk of scales and percentages with meaning”. When numbers are used appropriately in anthropological studies, they are not usually meant to provide the kind of certainty attached to the absolute values of biomedical research. The interest, rather, is in their relative values. Wallman and Baker,2 for example, show how a numerical index can be used qualitatively in so far as the analysis is primarily relational. Indeed, the difficulties Macnaughton outlines arise not with the inherent use of numbers, but with the interpretive truth, universality, and objectivity that statistical associations allegedly provide. Macnaughton argues that qualitative data are nonquantifiable because “the research is context specific”. Yet quantification bearing little relation to context leads researchers to consider indicators alone, thereby misinterpreting the dynamics between variables. As such, decontextualised research masks underlying variables that
Vol 348 • July 13, 1996
2
Macnaughton RJ. Numbers, scales, and qualitative research. Lancet 1996; 347: 1099–100. Wallman S, Baker M. Which resources pay for treatment? A model for estimating the informal economy of health. Soc Sci Med 1996; 42: 671–79.
Author’s reply SIR—Béhague and Ogden write as if they were disagreeing with me. But in so far as I can follow their argument they seem to be reaffirming some of the points I made. For example, I did not say that there are problems with the inherent use of numbers; my thesis is that the use of numbers in qualitative research suggests a false objectivity. Again, I entirely agree with them that decontextualised research masks underlying variables: that was one of my main points. Finally, my suggestion that understanding in qualitative research is more akin to the understanding gained from an art than from a science was not intended to “assert an antiquated argument” but merely to suggest an alternative way of looking at qualitative data—a way that I learned from the journals of my first degree studies in history and literature. Jane Macnaughton Department of General Practice, University of Glasgow, Glasgow G20 7LR, UK
SIR—Macnaughton1 raises fundamental issues about methods of clinical research but unfortunately perpetuates a serious misunderstanding. Qualitative research is conducted and reported by means of concepts—ie, verbally and without resort to numbers. It is increasingly promoted by medical journals as a way of understanding complex aspects of human behaviour, or organisations such as hospitals in situations in which quantification would be impossible or unhelpful.2 She specifically refers to studies of issues such as
127