Abstract
Background:
The inception of competency-based curricula in the medical education system of India has paved the way for student-centric, interactive teaching-learning methodologies such as problem-based learning (PBL) and self-directed learning (SDL).

Aim:
Because knowledge on osmolarity and body fluid balance has wide clinical applications, this study was conducted to determine the effectiveness of PBL and SDL in understanding the concept of osmolarity with volume–osmolarity diagram among first-year undergraduate medical students.

Method:
A total of 101 first-year undergraduate students were enrolled with informed consent. After the pre-test and briefing on the volume–osmolarity diagram, the participants were divided into Group 1 (n = 53) and Group 2 (n = 48). Group 1, with 8 subgroups, was given case scenarios and asked to illustrate findings in a volume–osmolarity diagram. Group 2 was guided to explore the topic with the necessary study material, followed by a post-test and feedback.

Results:
The mean post-test score (62.47 ± 19.21) significantly improved compared with the pre-test score (43.94 ± 12, p = 0.008). The mean pre-test scores between group 1 (44.54 ± 12.58) and group 2 (44.13 ± 13.33) was not statistically significant (p = 0.94), indicating that the students’ understanding of the subject was similar at the outset. No statistically significant differences (p = 0.66) were observed when post-test scores were compared between group 1 (60.57 ± 22) and group 2 (64.58 ± 18.69). The analysis of subjective feedback responses showed that the PBL group had more favorable outcomes for all items in the feedback questionnaire, some of which were statistically significant, when compared with the SDL group.

Conclusion:
The above-mentioned results show that PBL and SDL are equally effective in facilitating the learning of physiological concepts. However, its impact on medical education needs to be better studied and ascertained with a wider range of topics.

Key words: Problem-based learning; Self-directed learning; Volume–osmolarity diagram.