Nomogram for the Individualized Prediction of Survival Among Patients with H7N9 Infection

Abstract

Background

Until recently, almost all of these studies have identified multiple risk factors but did not offer practical instruments for routine use in predicting individualized survival in human H7N9 infection cases. The objective of this study is to create a practical instrument for use in predicting an individualized survival probability of H7N9 patients.

Methods

A matched case–control study (1:2 ratios) was performed in Zhejiang Province between 2013 and 2019. We reviewed specific factors and outcomes regarding patients with H7N9 virus infection (VI) to determine relationships and developed a nomogram to calculate individualized survival probability. This tool was used to predict each individual patient’s probability of survival based on results obtained from the multivariable Cox proportional hazard regression analysis.

Results

We examined 227 patients with H7N9 VI enrolled in our study. Stepwise selection was applied to the data, which resulted in a final model with 8 independent predictors [including initial PaO₂/FiO₂ ratio ≤300 mmHg, age ≥60 years, chronic diseases, poor hand hygiene, time from illness onset to the first medical visit, incubation period ≤5 days, peak C-reactive protein ≥120 mg/L], and initial bilateral lung infection. The concordance index of this nomogram was 0.802 [95% confidence interval (CI): 0.694–0.901] and 0.793 (95% CI: 0.611–0.952) for the training and validation sets, respectively, which indicates adequate discriminatory power. The calibration curves for the survival showed optimal agreement between nomogram prediction and actual observation in the training and validation sets, respectively.

Conclusion

We established and validated a novel nomogram that can accurately predict the survival probability of patients with H7N9 VI. This nomogram can serve an important role in counseling patients with H7N9 VI and guide treatment decisions.

Keywords:

• avian influenza virus
• H7N9
• survival
• predictors
• nomogram

Acknowledgment

We extend our gratitude to the individuals vital to executing this study. In particular, we thank the First Affiliated Hospital, School of Medicine, Zhejiang University and other designated hospitals of avian influenza A (H7N9) VI treatment in Zhejiang province for supplying clinical data and Hangzhou CDC’s field investigators for supplying epidemiological data.

Abbreviations

VI, virus infection; CDC, Center for Disease Control and Prevention; OR, odds ratio; CI, confidence interval; C-index, concordance index; PHH, poor hand hygiene; CD, chronic diseases; TIOFMV, time from illness onset to the first medical visit; IP, incubation period; CRP, C-reactive protein; IPFR, initial PaO₂/FiO₂ ratio; INP, initial neutrophil percentage; IBLI, initial bilateral lung infection; IWBCC, initial white blood cell count; ILP, initial lymphocyte percentage; IVH, initial value of hemoglobin; IBPC, initial blood platelet count.

Ethics and Consent Statement

We obtained ethical approval to carry out this study from the Institutional Review Board (IRB) of Hangzhou Center for Disease Control and Prevention, Hangzhou, China. The medical directors of the selected hospitals acknowledged this IRB and delivered their permission to start data collection. All patients or their relatives provided written informed consent for this research, which was carried out in compliance with the Helsinki Declaration. All individual information was strictly kept confidential and anonymous in the manuscript.

Author Contributions

QLC and ZS developed the study concept and supervised data collection. All authors were involved in the study design. QLC, GZ and LX analyzed the data with input from all authors. QLC drafted the initial manuscript. ZS and GZ provided input on early drafts. All authors contributed to data analysis and revising the article, gave final approval of the version to be published, and agree to be accountable for all aspects of the work.

Disclosure

The authors declare that they have no conflicts of interest in this work.

Additional information

Funding

This work is supported by the Medical Science and Technology Project of Zhejiang Province (grant number: 2020PY064) and the Health Science and Technology Project of Hangzhou Municipality (grant number: OO20190783).