marginally significantP value = 0.07
The percentages of changes for each reason were not significantly different during the studied time in the IMSS ( P value = 0.97) or in the SSA ( P value = 0.13), but it was marginally significant in the INS ( P value = 0.07), where the percentage of changes for toxicity decreased after 2001 (21% versus 14.8%) and changes for optimizing increased (39.1% versus 44.4%).