Impact of Online Safety Screening on Outpatient MRI Workflow

Author

Lu Mao

Statistical analysis

Quantitative variables (patient age, time to image) were summarized by mean (SD, standard deviation) and compared between groups by ANOVA, with Tukey’s post-hoc pairwise comparisons. Categorical variables (sex, post-arrival cancellation) were summarize by frequency (percent) and compared between groups by the chi-square test, with Bonferroni adjustment to post-hoc pairwise comparisons. P-values \(<\) 0.05 were considered statistically significant. All analyses were performed in R version 4.3.2 (R Foundation for Statistical Computing, Vienna, Austria).

Comparison between three groups

Patient age, sex, cancellation status (yes vs no), and time to image (min) are summarized in Table 1 by group: (1) before-traditional, (2) post-traditional, and (3) post-online, with post-hoc pairwise tests. Cancellation rate is significantly lower in post-online compared to before and post-traditional, but not between the latter two groups. Time to image for those without cancellation is significantly lower in post-traditional compared to before, and in post-online compared to post-traditional (see also Figure 1).

Table 1: Comparison between three groups with overall and post-hoc pairwise tests.
Before-Trad (N=5641) Post-Trad (N=4356) Post-Online (N=2730) Overall 1v2 2v3 1v3
Age (years) 53.9 (17.1) 56.5 (16.7) 54.5 (15.9) <0.001 <0.001 <0.001 0.267
Sex - Female 3113 (55.2%) 2354 (54%) 1594 (58.4%) 0.001 0.788 <0.001 0.016
Sex - Male 2528 (44.8%) 2002 (46%) 1134 (41.6%)
Cancel - No 5566 (98.7%) 4289 (98.5%) 2710 (99.3%) 0.012 1 0.012 0.063
Cancel - Yes 75 (1.3%) 67 (1.5%) 20 (0.7%)
Time to image (min) 39 (21.5) 37 (19.2) 35.3 (16.9) <0.001 <0.001 0.001 <0.001

Figure 1: Percentage of post-arrival cancellation and mean time to image by group.

Differences in time to image

The post-hoc 95% confidence intervals for between-group differences in time to image are tabulated in Table 2.

Table 2: Post-hoc analysis of pairwise differences in time to image (min).
Comparison Difference 95% CI P
Post-Trad - Before-Trad -2.0 (-3, -1.1) <0.001
Post-Online - Post-Trad -1.7 (-2.8, -0.6) 0.001
Post-Online - Before-Trad -3.7 (-4.8, -2.7) <0.001

Comparison pre vs post

Same analyses repeated for pre vs post.

Table 3: Comparison between pre and post groups.
Before (N=5641) Post (N=7086) P
Age (years) 53.9 (17.1) 55.7 (16.5) <0.001
Sex - Female 3113 (55.2%) 3948 (55.7%) 0.55
Sex - Male 2528 (44.8%) 3136 (44.3%)
Cancel - No 5566 (98.7%) 6999 (98.8%) 0.668
Cancel - Yes 75 (1.3%) 87 (1.2%)
Time to image (min) 39 (21.5) 36.3 (18.4) <0.001

Figure 2: Percentage of post-arrival cancellation and mean time to image by group.

Comparison of variances of time to image

Table 4: F-test comparing the variance (SD) of time to image between groups.
Groups SD df P
Before/Post 21.5/18.4 5565, 6998 <0.001
Before-Trad/Post-Online 21.5/16.9 5565, 2709 <0.001
Post-Trad/Post-Online 19.2/16.9 4288, 2709 <0.001