Table 2.

Modified reciprocal control design for a hypothetical trial with subjects having two of three potential risk factors (A, B or C). Within risk factor combination subjects are randomized to treatment and control for different risk factors. Different combinations of subjects contribute to effect estimation

Risk factor combination	Patient in arm with risk factor combination	Random assignment	Risk factors contributing to effect estimate
			A	B	C
AB	A patient with AB	Treatment A	X	X
		Control B
	Another patient with AB	Control A	X	X
		Treatment B
AC	A patient with AC	Treatment A	X		X
		Control C
	Another patient with AC	Control A	X		X
		Treatment C
BC	A patient with BC	Treatment B		X	X
		Control C
	Another patient with BC	Control B		X	X
		Treatment C