Occup Environ Med 62:743-749 doi:10.1136/oem.2004.016147
  • Original article

Surveillance for isocyanate asthma: a model based cost effectiveness analysis

  1. D M Wild1,
  2. C A Redlich2,
  3. A D Paltiel1
  1. 1Department of Epidemiology and Public Health, Yale University School of Medicine, New Haven, CT, USA
  2. 2Yale Occupational and Environmental Medicine Program, Department of Medicine, Yale University School of Medicine, New Haven, CT, USA
  1. Correspondence to:
 Dr D Wild
 Department of Internal and Preventive Medicine, Griffin Hospital, 130 Division Street, Derby, CT 06418, USA;
  • Accepted 10 May 2005


Aims: Because logistical and financial obstacles impede using large prospective cohort studies, surveillance decisions in occupational settings must often be made without evidence of relative benefits and costs. Using the example of isocyanate induced asthma, the most commonly reported immune mediated occupational asthma, the authors developed a model based approach to evaluate the costs and benefits of surveillance from both an employer and a societal perspective.

Methods: The authors used a mathematical simulation model of isocyanate asthma to compare annual surveillance to passive case finding. Outcome measures included symptom free days (SFD), quality adjusted life years (QALY), direct costs, productivity losses, and incremental cost effectiveness ratio (CER), measured from the employer and the societal perspectives. Input data were obtained from a variety of published sources.

Results: For 100 000 exposed workers, surveillance resulted in 683 fewer cases of disability over 10 years. Surveillance conferred benefits at an incremental cost of $24,000/QALY (employer perspective; $13.33/SFD) and was cost saving from the societal perspective. Results were sensitive to assumptions about sensitisation rate, removal rates, and time to diagnosis, but not to assumptions about therapy costs and disability rates.

Conclusions: Baseline results placed the CER for surveillance for isocyanate asthma within the acceptable range. Costs from the societal and employer perspective differed substantially with a more attractive CER from the societal perspective, suggesting opportunities for employer/societal cost sharing. The analysis demonstrates the value of a model based approach to evaluate the cost effectiveness of surveillance programmes for isocyanate asthma, and to inform shared decision making among clinicians, patients, employers, and society. Such a modeling approach may be applicable to surveillance programmes for other work related conditions.


  • Funding sources: CDC/NIOSH Grant 1R01OH03457, NIH/NIEHS grant K24-ES00355

  • Results of our model have been presented as an oral presentation at Medical Decision Making 2003 and ATS and are published as an abstract in Medical Decision Making2003;: and in the Am J Respir Crit Care Med2004;:.

  • As this study did not involve direct patient contact, we did not need institutional ethics committee approval.