Last update:
11-Nov-2004

The treatment threshold probability after clinical examination is by definition the disease probability when the expected value of treatment is equal to the expected value of no treatment-“attentive waiting”. The outcomes are distinguished proportionately by the number and the content into dichotomous and polytomous. In dichotomous outcomes with zero value (i.e. death) the treatment threshold after clinical examination (P*) will be: P*=1/ (B/C+1), while in dichotomous outcomes with a value other than or in polytomous outcomes, the treatment threshold after clinical examination is connected with the expected benefit (EB) and expected harm (EC) as follows: P*=1/(EB/EC+1). In a clinical problem with diagnostic uncertainty the following formulae apply: (a) If P(D⁺)>P* and EV(Rx⁺)>EV(Rx^–), then the treatment is certain. (b) If P(D+)< P* and EV(Rx⁺) >EV(Rx^–), then no treatment or “attentive waiting” is the preferable solution. (c) If P(D⁺)< P* and EV(Rx⁺)>EV(Rx^–), then treatment is not given, but an attempt is made with diagnostic test or tests to increase the probability of disease presence (the positive predictive value of test to approach a). (d) If P(D⁺)>P* and EV(Rx⁺)< EV(Rx^–), then treatment is not given, but reinvestigation of literature is indicated for the existence of random error in the “predominance” treatment choice, and (e) if P(D⁺)=P* and EV(Rx⁺EV(Rx^–), then the principle of indifference applies. If treatment is applied, for each patient who is correctly treated, P(D⁺)/P(D^–) non-patients will be treated mistakenly.>

Key words: Clinical, Decision, Probability, Threshold, Treatment.