Correlation between patients’ reasons for encounters/health problems and population density in Japan: a systematic review of observational studies coded by the International Classification of Health Problems in Primary Care (ICHPPC) and the International Classification of Primary care (ICPC)

In 2013, the Ministry of Health, Labour and Welfare highlighted the importance of the primary care physician in the rapidly aging society of Japan [1]. However, in Japan, a boundary between primary care and secondary care is ambiguous due to free-access system [2] and there are many specialist clinics (e.g., ophthalmological clinic) which deal with health problems of each discipline [3]. In addition, the Japanese health care system has yet to establish structured training for primary care physicians; therefore, physicians who received an internal medicine based training program continue to play a principal role in the primary care setting [3].

To promote the development of a more efficient primary health care system, the assessment of its current status in regard to the spectrum of patients’ reasons for encounters (RFEs) and health problems is an important step [4]. However, the International Classification of Diseases 10th revision (ICD-10) does not include a classification for RFEs or the health problems of unsolved problems [5, 6], which makes it inconsistent with the primary care setting. Therefore, the International Classification of Primary Care 2nd edition (ICPC-2) is recommended for use in primary care[7]^. Although several descriptive surveys utilizing ICPC-2 have been conducted in Japan [4], there has been no systematic review which target surveys using ICPC-2. For example, recognizing the proportions of patients’ RFEs and health problems, which are not generally covered by an internist, can provide valuable information to promote the development of a primary care physician-centered system. In addition, Miyazaki presumed that the less accessibility patients have to a specialist clinic and/or a secondary care hospital, the more diverse their RFEs and health problems in the primary care setting [4].

This study aimed to describe the diversity of RFEs and health problems in Japanese settings of primary care. We also examined a correlation between the proportions of non-internal medicine related RFEs/health problems and population density as index of accessibility.

After searching through the titles and abstracts of 4275 publications, 17 eligible publications were identified (Fig. 1). Details about the included studies [16‐32] are shown in Additional file 1: Table S1 and the characteristics of those studies are shown in Table 4.

In these studies, “non-internal medicine-related” RFEs, which was not thought to be covered by internists, varied from approximately 4% to 40%. In addition, “non-internal medicine-related” health problems varied from 10% to 40%. The proportion of “non-internal medicine-related” RFEs reached 41.4% in a study set in rural area. Moreover, the proportion of “non-internal medicine-related” health problems reached 45.4% in another study of rural setting.

The relationship between the proportion of “non-internal-medicine-related” RFEs among all RFEs and population density is shown in Fig. 2a, while that between “non-internal-medicine-related” health problems among all health problems and population density is shown in Fig. 2b. We used “RFEs in the first visit” for Fig. 2a and statistical analysis because most studies described only RFEs in the first visit. Five studies in which all health problems (all health problems: combination of acute and chronic health problems) had not been described were excluded from Figure2b and statistical analysis. We used Spearman’s rank correlation coefficient to investigate for the presence of a dependence between RFEs/health problems and population density. In Fig. 2a, there seems to be negative correlation between proportion of non-internal medicine related RFEs and population density. However, no statistically significant correlations were found (p = 0.20): Spearman’s rank correlation coefficient was −0.80 (95% Confidence Interval: −0.998 to 0.507). Also, the correlation between health problems and population density was not statistically significant (p = 0.74): Spearman’s rank correlation coefficient was −0.14 (95% Confidence Interval: −0.678 to 0.729).

The current systematic review detected 17 studies coded by ICHPPC and ICPC in Japan with diversity in both study design and settings.

In Japan, even in the primary-care setting, the proportion of “non-internal medicine-related” RFEs varies tremendously. In contrast, in other countries with an advanced primary care system, primary care physicians manage more “non-internal medicine-related” RFEs and health problems [33]. The differences between these countries and Japan in the proportion of RFEs are likely due to the Japanese free access system. In Japan, a patient can visit a specialist freely as a first encounter. A primary-care clinic located near a facility with a specialist does not need to manage “non-internal medicine-related” RFEs and health problems. For example, one of the included study [24] in urban area described the non-internal medicine related health problems were only 11.4%. However, in some studies in rural area, the percentage of “non-internal medicine-related” RFEs or health problems reached over 40% [20, 22, 25, 31]. Therefore, to refine and improve the educational system for aspiring generalists in Japan, curriculum with “non-internal medicine-related” practical training should be emphasized.

The shortage of studies in urban or suburban areas may partly explain the lack of a significant correlation between “non-internal medicine-related” RFEs/health problems and population density. For instance, most of the studies (13/17) using ICHPPC and ICPC were carried out in rural areas. In contrast, only two of the studies were conducted in an urban setting. In addition, only 2 studies described the evaluator’s experience of attending ICPC-coding training program, though the quality of data collection is said to be important when using data from patient records such as ICPC [34]. Japanese primary care physicians might obtain more-precise picture by considering surveys in diverse areas and quality of methodology.

It is also important to note that far fewer Japanese studies use ICPC data for purposes such as health care policy and medical education compared with other countries using ICPC data [32, 35‐38]. For example, in the Netherlands, more than 300 studies have been conducted from the existing ICPC database [39].

The current study has some limitations. First, population density could only be measured retrospectively. It was not possible to consider detailed medical circumstances such as the existence of a nearby specialist clinic and/or the distance to a secondary care hospital. These factors likely had an impact on RFEs and health problems. Second, to ensure quality, only original articles published in peer-reviewed journals were included in the present systematic review. Conference presentations and unpublished articles that were excluded from this study may contain additional research conducted in urban areas or in multiple facilities. Third, unfortunately, the type of doctors (internist/primary care physicians) and the type of training were not described in the studies included by our systematic review. Fourth, the distinction between internal medicine and non-internal medicine was not judged based on actual patient behavior under the situation that the care by various specialists was easily available. The distinction was only based on the decision by the two of the authors. In addition, whether patients with non-internal medicine related RFEs/health problems choose primary care physicians or specialists, i.e. orthopedics might depend on type of training which a physician received (internist/primary care physician). If some internists in the researches included by our systematic review acquired the knowledge and skills of primary care physician by self-directed learning, however, the proportion of non-internal medicine related RFEs and health problems might be overestimated for internists in general.

In conclusion, the findings of review suggest that the ability to deal with “non-internal medicine-related” RFEs and health problems is required for primary care physicians in some rural areas of Japan. In addition, curriculum need to be combined with “non-internal medicine-related” practical training to foster aspiring generalists. We expect these findings to help facilitate improvements in the early stages of the educational system for generalists. More studies focusing on ICPC should be conducted in the future in order to better understand the current status of primary care in Japan.

Although the study was regionally limited, its result may suggest that a training system for primary care physicians to deal with a variety of RFEs and health problems is important even in countries not having gatekeeping function by primary care physician such as Japan.