Development and Validation of a Simple-to-Use Nomogram for Predicting 5-, 10-, and 15-Year Survival in Asymptomatic Adults Undergoing Coronary Artery Calcium Scoring

Abstract

Objectives: The purpose of this study was to develop and validate a simple-to-use nomogram for prediction of 5-, 10-, and 15-year survival among asymptomatic adults.

Background: Simple-to-use prognostication tools that incorporate robust methods such as coronary artery calcium scoring (CACS) for predicting near-, intermediate- and long-term mortality are warranted.

Methods: In a consecutive series of 9,715 persons (mean age: 53.4 ± 10.5 years; 59.3% male) undergoing CACS, we developed a nomogram using Cox proportional hazards regression modeling that included: age, sex, smoking, hypertension, dyslipidemia, diabetes, family history of coronary artery disease, and CACS. We developed a prognostic index (PI) summing the number of risk points corresponding to weighted covariates, which was used to configure the nomogram. Validation of the nomogram was assessed by discrimination and calibration applied to a separate cohort of 7,824 adults who also underwent CACS.

Results: A total of 936 and 294 deaths occurred in the derivation and validation sets at a median follow-up of 14.6 years (interquartile range: 13.7 to 15.5 years) and 9.4 years (interquartile range: 6.8 to 11.5 years), respectively. The developed model effectively predicted 5-, 10-, and 15-year probability of survival. The PI displayed high discrimination in the derivation and validation sets (C-index 0.74 and 0.76, respectively), indicating suitable external performance of our nomogram model. The predicted and actual estimates of survival in each dataset according to PI quartiles were similar (though not identical), demonstrating improved model calibration.

Conclusions: A simple-to-use nomogram effectively predicts 5-, 10- and 15-year survival for asymptomatic adults undergoing screening for cardiac risk factors. This nomogram may be considered for use in clinical care.

Keywords: all-cause mortality; coronary artery calcium scoring; nomogram; prediction.

Figure 1. Instructions for using the nomogram

Draw a line perpendicular from the corresponding axis of each risk factor until it reaches the top line labeled “POINTS”. Sum up the number of points for all risk factors then draw a line descending from the axis labeled “TOTAL POINTS” until it intercepts each of the survival axes to determine 5-, 10-, and 15-year survival probabilities. For binary variables, 0 = no and 1 = yes. For CACS categories, 0 = none, 1 = 1–100, 2 = 101–400, 3 = 401–1,000, and 4 = >1,000. Abbreviations: CAD = coronary artery disease; CACS = coronary artery calcium score.

Figure 2. Comparison of the discrimination between derivation (solid lines) and validation (dashed lines) sets according to quartiles of the prognostic score

Visual comparisons between the study sets were derived from a Kaplan-Meier survival curve.

Figure 3. Calibration plot of a Cox model for the derivation and validation sets according to quartiles of the prognostic score

Smooth solid lines are predicted probabilities and vertical capped lines are Kaplan-Meier (observed) estimates with 95% confidence intervals. Darkest gray = Quartile 1; medium-dark gray = Quartile 2; light gray = Quartile 3; lightest gray = Quartile 4.