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This presentation reviews the U.K. experience of computer-aided diagnosis of acute abdominal pain--which now relates to over 30,000 cases seen in more than 10 hospitals during a 13 years period. Following a discussion of the philosophy, construction and mode of usage of the systems employed, results of this experience are presented. Computer-aided diagnosis in this area has been shown to be feasible and (if correctly utilised) leads to improvements in patient care, diagnosis, and decision making by the doctors involved. In this context, the computer is simply one element of an integrated package reaffirming the importance of traditional clinical medicine.

By 1982, the central analysis team of this on-going multinational survey had received a total of 8,723 cases for analysis and had accepted 8,480. In all some 23 centres in 15 countries, involving over 200 doctors had participated in this survey. A common protocol was used for data collection; around 98% of all possible data was recorded (using pre-circulated definitions) and analysed via a computer-aided system in Leeds, England. As before, the most common surgical diagnosis was acute appendicitis (2336 of 8,480 cases, 27.5%) followed by acute cholecystitis (800 cases, 9.4%). The construction of a worldwide database of information about 6.097 patients is described--as is its use both in diagnosis and in teaching. Particular attention is given to the construction of a computer program which allows medical students to compare their impression of acute abdominal pain with 'reality' as evidenced in these 6,097 patients. As regards additional cases, particular stress has been laid on acquisition of material from countries outside Europe and North America. Series from Mexico (893 patients) and Thailand (311 patients) are discussed in detail, and the implications for future work are reviewed.

This paper describes the use of a system of computer aided diagnosis in an unselected, prospective survey of 393 women suffering from lower abdominal pain of less than 1 week's duration. An accurate diagnosis was made by clinicians at first patient contact in 68-5 per cent of the group of patients. The computer's diagnostic prediction (based on the same data) matched the final diagnosis in 81-6 per cent of the patients. During this survey a marked improvement in diagnostic accuracy was observed amongst the junior clinicians. It is suggested that this is because of the discipline of data collection imposed and the intermittent feedback received, and also that this educational aspect of computer usage may be of wider benefit.

This paper assesses the extent and importance of geographical variation in disease presentation in relation to automated systems for clinical decision making. Reference is made to studies carried out by the World Organization of Gastroenterology involving 1,500 patients with inflammatory bowel disease, 6,000 patients with acute abdominal pain, and 1,300 patients with upper GI bleeding. These studies indicate that geographical variation in disease presentation (both regarding prior probability of disease and conditional probability of symptoms in each disease) is so great as to constitute a considerable potential threat to the widespread introduction of any automated decision-making system. It is suggested that there is an urgent need for the creation of large-scale multinational case series where diseases and symptoms are adequately and reproducibly defined in advance. Reference to studies previously mentioned is used to adduce evidence of the benefits of such large-scale data bases.

A multicentre study of computer aided diagnosis for patients with acute abdominal pain was performed in eight centres with over 250 participating doctors and 16,737 patients. Performance in diagnosis and decision making was compared over two periods: a test period (when a small computer system was provided to aid diagnosis) and a baseline period (before the system was installed). The two periods were well matched for type of case and rate of accrual. The system proved reliable and was used in 75.1% of possible cases. User reaction was broadly favourable. During the test period improvements were noted in diagnosis, decision making, and patient outcome. Initial diagnostic accuracy rose from 45.6% to 65.3%. The negative laparotomy rate fell by almost half, as did the perforation rate among patients with appendicitis (from 23.7% to 11.5%). The bad management error rate fell from 0.9% to 0.2%, and the observed mortality fell by 22.0%. The savings made were estimated as amounting to 278 laparotomies and 8,516 bed nights during the trial period--equivalent throughout the National Health Service to annual savings in resources worth over 20m pounds and direct cost savings of over 5m pounds. Computer aided diagnosis is a useful system for improving diagnosis and encouraging better clinical practice.

This paper reports a controlled trial of human and computer-aided diagnosis in a series of 552 patients with acute abdominal pain. The overall diagnostic accuracy of the computer-aided system was 91.5% and that of the senior clinician to see each case was 81.2%. However, the clinician's diagnostic performance improved markedly during the period of the trial. The proportion of appendices which perforated before operation fell from 36% to 4% during the trial, and the negative laparotomy rate dropped sharply. After the trial closed in August 1972 these figures reverted towards their pretrial levels.It is suggested that while computer-aided diagnosis is a valuable direct adjunct to the clinician dealing with the "acute abdomen," he may also benefit in the short-term from the constant feedback he receives and from the disciplines and constraints involved in communicating with the computer.