Variability in knowledge retention of medical students: repeated and recently learned basic science topics

Basic science knowledge is essential for understanding clinical studies and enhancing clinical reasoning in medical practice. However, medical students retain only a portion of the knowledge gained during the early years of medical school. We aimed to examine medical students' knowledge retention of repeated and recently learned topics in physiology and microbiology with additional analysis of individual variability. Given that prior studies have raised concerns about the validity of retention rate as an indicator of stable knowledge, we also explored alternative measures of retention.

Nineteen third- and 22 fourth-year medical students volunteered to repeat the written examinations in physiology and microbiology, respectively, in September 2022 at the University of Pécs. Students previously completed a summative test in the fall semester and another test in the spring semester. Both examinations consisted of multiple-choice questions and the second test included questions from both semesters introducing a unique form of spaced repetition. In our study, students repeated the complete second test after a 16-week non-use retention interval. Besides retention rates, we calculated the percentage of consistently correct and incorrect answers as retention measures. Correlations between retention measures and students' grade point averages (GPAs) were examined.

Significant declines in test scores were observed, with physiology scores dropping from 70.4 to 53.5% and microbiology scores from 72.1 to 57.3%. Retention rates varied significantly, with values ranging from 54.5 to 97.2%. Microbiology revealed better results of first-semester content compared to the second semester in some of the retention measures, while physiology showed no difference between semesters. Retention rates did not correlate with GPA, however, the percentage of consistently correct answers showed moderate positive correlations, while the consistently incorrect answers showed moderate negative correlations with GPA.

There was a substantial knowledge loss among medical students with high individual variability indicating the need to explore factors affecting long-term knowledge retention in real-life educational settings more deeply. Previously acquired knowledge in microbiology demonstrated superior retention, potentially attributable to the beneficial effects of spaced repetition. The lack of correlation between retention rates and GPA suggests that other measures may better reflect stable knowledge.