Table 3.

Interactions of BRAF V600E With Conventional Risk Factors in Recurrence of PTC (all types): Synergy Test

Risk Factor for Interaction With BRAF V600E	Synergy Index*	95% CI
Patient age ≥ 45 years	3.22	0.69 to 15.01
Patient age ≥ 60 years	2.15	1.11 to 4.19
Lymph node metastasis	1.10	0.80 to 1.49
Extrathyroidal invasion	1.12	0.76 to 1.66

NOTE. Test method from Hosmer and Lemeshow.²⁸

Abbreviation: PTC, papillary thyroid cancer.

^*Synergy index different than 1 represents significant additive interaction; > 1 represents synergism; < 1 represents antagonism. There was significant synergistic interaction between BRAF V600E mutation and patient age ≥ 60 years in affecting recurrence of PTC. There were no significant interactions between BRAF V600E mutation and patient age ≥ 45 years, lymph node metastasis, or extrathyroidal invasion.