PPT Slide

• Threshold approach. Can a threshold (specific to each decision) be used to clarify the meaning of NNT?
  • In a decision model comparing two options, which has several variables, a threshold can be found on any of those variables.
  • Earlier examples of thresholds.
    • Treatment threshold on probability a patient has disease, in combination with sensitivity and specificity of a diagnostic test, yield No test/Test and Test/Treat thresholds for pretest probability (Pauker and Kassirer, 1980; extended to two dichotomous tests by Hershey and colleagues, 1986).
      • Treatment threshold depends on balancing gains and losses of acting, that is, setting EUtreat = EUno_treat. (See bgphthut.xl4 calculator downloadable from http://www.fammed.ouhsc.edu/robhamm/cdmcalc.htm.)
    • Treatment threshold on utility of the bad outcome, in combination with sensitivity and specificity of a diagnostic test and pretest probability, yield No-test/Test and Test/Treat thresholds for utility of the bad outcome (Nease and Bonduelle, 1987).
    • Threshold on NNT was used to determine whether the studies in a meta-analysis equivocally or unequivocally support using a treatment (Guyatt et al, 1995).
      • NNT threshold was defined by balancing costs of treatment with costs of, and WTP to avoid, both the bad outcome and adverse effects.

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