Case reports of adverse effects of herbal medicinal products (HMPs): a quality assessment

Case reports provide essential information on adverse effects. Yet there is little consistency in the quality and format of reporting them.

In this study, we aimed to assess the quality of case reports of adverse effect of herbal medicinal products (HMPs) published during three time periods, 1986-1988, 1996-1998, and 2006-2008.

We conducted literature searches in four major databases: Medline, EMBASE, AMED, and CINALH. Each case report was subject to specific inclusion criteria related to the intervention (i.e. herbal medicine) and outcome measurement (i.e. adverse effect). A 21-item scale was used to assess the quality of all included reports. Each report was categorised into low quality (score between 0 and 14), lower medium quality (score between 15 and 21), upper medium quality (score between 22 and 28), and high quality (score between 29 and 42).

In total, 137 case reports were included. The percentage of high quality case reports rose from 0% in 1986-1988 to 27.9% in 1996-1998 and 34.2% in 2006-2008; conversely, the percentages of low quality case reports dropped from 13.3% in 1986-1988 to 0% in 1996-1998 and 2.5% in 2006-2008.

These findings are consistent with the notion that the quality of case reports is improving. However, due to several caveats, our data should be interpreted with caution.