Table 4.

Ability of the Pharmacogenetic and Clinical Algorithms to Correctly Identify Patients Requiring Low or High Doses of Warfarin.

Actual or Predicted Dose Group	≤21 mg/wk		≥49 mg/wk
	Pharmacogenetic Algorithm	Clinical Algorithm	Pharmacogenetic Algorithm	Clinical Algorithm
Validation cohort
No. of patients predicted to require extreme dose	232	162	48	15
No. of patients actually requiring extreme dose	324	324	125	125
No. of patients correctly predicted to require extreme dose	160*	108	31*	9
Percent of patients correctly predicted to require extreme dose†	49.4	33.3	24.8	7.2
Derivation-plus-validation cohort
No. of patients predicted to require extreme dose	1250	829	243	98
No. of patients actually requiring extreme dose	1711	1711	625	625
No. of patients correctly predicted to require extreme dose	929*	571	165	57
Percent of patients correctly predicted to require extreme dose†	54.3	33.4	26.4	9.1

^*P<0.001 for the comparison of the pharmacogenetic algorithm with the clinical algorithm, with the use of a two-tailed sign test.

^†This value represents the number of patients correctly predicted to require the extreme dose divided by the number of patients who actually required the extreme dose.