title: Traumatic transfers: calibration is adversely affected when prediction models are transferred between trauma care contexts in India and the United States.
abstract: We evaluated the transferability of prediction models between trauma care contexts in India and the United States and explored updating methods to adjust such models for new contexts.
  
  
  
  Using a combination of prospective cohort and registry data from 3,728 patients of Towards Improved Trauma Care Outcomes in India (TITCO) and from 18,756 patients of the US National Trauma Data Bank (NTDB), we derived models in one context and validated them in the other, assessing them for discrimination and calibration using systolic blood pressure, heart rate, and Glasgow coma scale as candidate predictors.
  
  
  
  Early mortality was 8% in the TITCO and 1-2% in the NTDB samples. Both models discriminated well, but the TITCO model overestimated the risk of mortality in NTDB patients, and the NTDB model underestimated the risk in TITCO patients.
  
  
  
  Transferability was good in terms of discrimination but poor in terms of calibration. It was possible to improve this miscalibration by updating the models' intercept. This updating method could be used in samples with as few as 25 events.
authors.affiliation: Health Systems and Policy, Department of Public Health Sciences, Karolinska Institutet, SE-171 77 Stockholm, Sweden. Electronic address: martin.gerdin@ki.se.
authors.forename: Martin
authors.initials: M
authors.lastname: Gerdin
authors.affiliation: Health Systems and Policy, Department of Public Health Sciences, Karolinska Institutet, SE-171 77 Stockholm, Sweden; Department of Surgery, Bhabha Atomic Research Centre Hospital, Mumbai, Maharashtra 400085, India; School of Habitat, Tata Institute of Social Sciences, Chembur, Mumbai, Maharashtra 400088, India.
authors.forename: Nobhojit
authors.initials: N
authors.lastname: Roy
authors.affiliation: Division of Orthopedics and Biotechnology, Department of Clinical Science Intervention and Technology, Karolinska Institutet, Alfred Nobels allé 8, SE-141 52 Huddinge, Sweden.
authors.forename: Li
authors.initials: L
authors.lastname: Felländer-Tsai
authors.affiliation: Health Systems and Policy, Department of Public Health Sciences, Karolinska Institutet, SE-171 77 Stockholm, Sweden; Department of Learning, Informatics, Management and Ethics, Karolinska Institutet, SE-171 77 Stockholm, Sweden.
authors.forename: Göran
authors.initials: G
authors.lastname: Tomson
authors.affiliation: Health Systems and Policy, Department of Public Health Sciences, Karolinska Institutet, SE-171 77 Stockholm, Sweden.
authors.forename: Johan
authors.initials: J
authors.lastname: von Schreeb
authors.affiliation: Centre for Applied Biostatistics, Occupational and Environmental Medicine, Sahlgrenska Academy, University of Gothenburg, PO Box 414, SE-405 30 Gothenburg, Sweden; School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, 7 York Rd, Johannesburg 2193, South Africa.
authors.forename: Max
authors.initials: M
authors.lastname: Petzold
authors.affiliation: Jai Prakash Narayan Apex Trauma Center, All India Institute of Medical Sciences, New Delhi, Delhi 110029, India.
authors.forename: Amit
authors.initials: A
authors.lastname: Gupta
authors.affiliation: Jai Prakash Narayan Apex Trauma Center, All India Institute of Medical Sciences, New Delhi, Delhi 110029, India.
authors.forename: Ashish
authors.initials: A
authors.lastname: Jhakal
authors.affiliation: Institute of Post-Graduate Medical Education and Research and Seth Sukhlal Karnani Memorial Hospital, Harish Mukherjee Rd, Bhowanipore, Kolkata, India.
authors.forename: Debojit
authors.initials: D
authors.lastname: Basak
authors.affiliation: Department of Orthopedics, Madras Medical College, Chennai, Tamil Nadu 600003, India.
authors.forename: Deen
authors.initials: D
authors.lastname: Mohamed Ismail
authors.affiliation: Jai Prakash Narayan Apex Trauma Center, All India Institute of Medical Sciences, New Delhi, Delhi 110029, India.
authors.forename: Dusu
authors.initials: D
authors.lastname: Yabo
authors.affiliation: Madras Medical College, Chennai, Tamil Nadu 600003, India.
authors.forename: K
authors.initials: K
authors.lastname: Jegadeesan
authors.affiliation: King Edward Memorial Hospital, Mumbai, Maharashtra 400012, India.
authors.forename: Jyoti
authors.initials: J
authors.lastname: Kamble
authors.affiliation: Department of Surgery, Institute of Post-Graduate Medical Education and Research and Seth Sukhlal Karnani Memorial Hospital, Harish Mukherjee Rd, Bhowanipore, Kolkata, India.
authors.forename: Makhan Lal
authors.initials: ML
authors.lastname: Saha
authors.affiliation: Lokmanya Tilak Municipal Medical College and General Hospital, Mumbai, Maharashtra 400022, India.
authors.forename: Mangesh
authors.initials: M
authors.lastname: Nitnaware
authors.affiliation: General Surgery, Seth GS Medical College & King Edward Memorial Hospital, Mumbai, Maharashtra 400012, India.
authors.forename: Monty
authors.initials: M
authors.lastname: Khajanchi
authors.affiliation: Department of Neurosurgery, Madras Medical College, Chennai, Tamil Nadu 600003, India.
authors.forename: Ranganathan
authors.initials: R
authors.lastname: Jothi
authors.affiliation: Department of Neurosurgery, Institute of Post-Graduate Medical Education and Research and Seth Sukhlal Karnani Memorial Hospital, Harish Mukherjee Rd, Bhowanipore, Kolkata, India.
authors.forename: Samarendra Nath
authors.initials: SN
authors.lastname: Ghosh
authors.affiliation: Jai Prakash Narayan Apex Trauma Center, All India Institute of Medical Sciences, New Delhi, Delhi 110029, India.
authors.forename: Sanjeev
authors.initials: S
authors.lastname: Bhoi
authors.affiliation: Jai Prakash Narayan Apex Trauma Center, All India Institute of Medical Sciences, New Delhi, Delhi 110029, India.
authors.forename: Santosh
authors.initials: S
authors.lastname: Mahindrakar
authors.affiliation: Department of Surgery, Lokmanya Tilak Municipal Medical College and General Hospital, Mumbai, Maharashtra 400022, India.
authors.forename: Satish
authors.initials: S
authors.lastname: Dharap
authors.affiliation: Department of Surgery, King Edward Memorial Hospital, Mumbai, Maharashtra 400012, India.
authors.forename: Shilpa
authors.initials: S
authors.lastname: Rao
authors.affiliation: Madras Medical College, Chennai, Tamil Nadu 600003, India.
authors.forename: Veera
authors.initials: V
authors.lastname: Kamal
authors.affiliation: Department of Surgery, Lokmanya Tilak Municipal Medical College and General Hospital, Mumbai, Maharashtra 400022, India.
authors.forename: Vineet
authors.initials: V
authors.lastname: Kumar
authors.affiliation: School of Habitat, Tata Institute of Social Sciences, Chembur, Mumbai, Maharashtra 400088, India.
authors.forename: Santosh
authors.initials: S
authors.lastname: Tirlotkar
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001794:Blood Pressure; D002138:Calibration; D015331:Cohort Studies; D005260:Female; D015600:Glasgow Coma Scale / Q000706:statistics & numerical data; D006339:Heart Rate; D006801:Humans; D007194:India / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D017063:Outcome Assessment, Health Care / Q000379:methods / Q000706:statistics & numerical data*; D011446:Prospective Studies; D012042:Registries; D014481:United States / Q000453:epidemiology; D014947:Wounds and Injuries / Q000453:epidemiology* / Q000628:therapy*
keywords: Calibration; Discrimination; Global health; Prediction modeling; Transferability; Trauma