Development and validation of a dynamic nomogram for SPTB at
< 32 weeks
Based on meaningful independent factors in multivariate regression
analysis, we developed a nomogram to predict the SPTB probability at
< 32 weeks (Figure 2). Each point could be determined based on
the intersection of the vertical line from the variable to the point
axis. Then, the total risk score was calculated by adding each variable
point. The possibility of twin SPTB at <32 weeks could be read
on the total point axis.
Furthermore, a user-friendly dynamic predicative nomogram was
established and available
online(https://zhanwenqiang.shinyapps.io/DynNomapp/). The dynamic
nomogram conveniently provided individual probability of SPTB which was
calculated automatically by the input characteristics of each subject
(Supplementary Figure 2). The Harrell’s concordance index value of the
nomogram model in the training group was 0.856 (95%CI: 0.813-0.899).
Calibration plots demonstrated that the nomogram was well calibrated,
with favourable agreement between the nomogram-predicted probabilities
and the actual probabilities of SPTB at <32 weeks
(Supplementary Figure 3A). When applied to the external validation
group, the Harrell’s concordance index value of the nomogram model in
the external group was 0.808 (95%CI: 0.751-0.865). The calibration
curves indicated that the probability predicted by the nomogram was in
good agreement with the actual observation results (Supplementary Figure
3B).