Diagnosing heart failure in primary health care

Abstract

Diagnosing chronic heart failure (CHF) is difficult. General practitioners (GPs) have an important role in the management of heart failure patients, and the purpose of the studies was to examine their judgements of patients with suspected CHF. Two methods from cognitive psychology were used, Clinical Judgement Analysis (CJA) in Studies I-IV, and think-aloud technique in Study V. Written case vignettes based on authentic patients were presented either in a paper format (Studies 1-111) or on a computer screen (Study V). In Study IV, theoretical and practical problems concerning how to construct suitable case vignettes for CJA studies were discussed, with reference to experiences from Studies I-II.

In Study I, 27 GPs assessed the probability of CHF for 45 case vignettes, five of which were duplicates. Each GP's diagnostic strategy was defined as the set of statistical regression weights for the different variables (cues) describing the patient. Both judgements and strategies varied widely among the GPs, but according to analysis of the duplicate cases, the GPs were consistent in their judgements. The most important cues were pulmonary congestion and cardiac volume.

In Study 11, 27 GPs, 22 cardiologists and 21 medical students assessed the probability of CHF for 40 case vignettes. Since the diagnoses were based on thorough investigations and cardiologists' judgements ("gold standard"), diagnostic accomplishment could be analysed. The variation was large regarding strategies and diagnostic accomplishment between individuals, but not between the groups. The most important cues were cardiac volume and pulmonary congestion. Using cluster analysis, three main strategies were identified. Cardiac volume dominated in the first, pulmonary congestion in the second, and in the third the weights were more evenly distributed. The first cluster, comprising a third of the participants, had the best diagnostic accomplishment.

In Study III, the same data were analysed for characteristics of the case vignettes causing the most and the least diagnostic agreement among the participants. Increased cardiac volume and presence of atrial fibrillation contributed to the diagnostic agreement between the participants, as well as a larger number of cues indicative of CHF. The starting point for Study IV was the recommendation in the CJA literature to use representative case vignettes. The concept of representativity and its consequences for the construction of case vignettes were discussed. Two factors above all turned out to be problematic: the incomplete information in the patient records and the necessity of keeping the number of case vignettes low. These two factors necessitated compromises regarding, for example, the choice of cues and the number of cues.

In Study V, 15 GPs judged six case vignettes, selected from Study 11, and the data were analysed regarding how different kinds of information were used in the diagnostic judgements. Although echocardiography (not included in the previous studies) was the most frequently used information, it was not used in a third of the judgement situations. Cardiac volume and pulmonary congestion were also important information. Information about other relevant diseases was frequently used in the diagnostic reasoning, but this is not reflected in the guidelines.

Both of the two methodological approaches to diagnostic judgements and reasoning in this thesis are useful tools for studying clinical decision-making. One possible application area is the study of expert doctors and medical students, which can give insights useful for teaching. Other application areas involve the development and testing of different decision support systems integrated in electronic patient records, and the development of guidelines.