Table C.7Probabilities

VariableValueSourceNotes
Weekly breakage/loss of hearing aid0.0031GDG estimateEstimated that 25% would lose/break their hearing aid within initial resolution period (21 months).a
Re-insertion rate (second tube)0.25GDG estimateAt baseline this is assumed to be identical for both surgical procedures, but this assumption can be relaxed as part of a sensitivity analysis.
Re-insertion (third tube)0.25GDG estimateAt baseline this is assumed to be identical for both surgical procedures, but this assumption can be relaxed as part of a sensitivity analysis.
Removal of ventilation tubes0.07Hospital Episode Statistics, DH (2005–06)Insertion procedures 31 818
Removal procedures 2149
a

The probability of weekly breakage/loss is calculated as an instantaneous event rate. The formula to derive an instantaneous event rate from a probability over a period of time is:

r = -[ln(1-P]/t

In our case, the instantaneous event rate (events per week) is:

r = -[ln(0.75)]/91 = 0.0031

From: Appendix C, Economic evaluation of alternative management strategies for OME in children

Cover of Surgical Management of Otitis Media with Effusion in Children
Surgical Management of Otitis Media with Effusion in Children.
NICE Clinical Guidelines, No. 60.
National Collaborating Centre for Women’s and Children’s Health (UK).
London: RCOG Press; 2008 Feb.
Copyright © 2008, National Collaborating Centre for Women’s and Children’s Health.

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