I am currently trying to examine the effect of of NCV's on gene expression in known cardiomyopathy genes (BRAF, FKTN, TGFB3)

qRT-PCR was performed with RNA from the patients with confirmed NCVs in the above mentioned genes against 3 healthy controls. GAPDH was used as the reference gene and CT data shows stable expression across both controls and test samples.

I plan to use the double delta CT method to examine relative gene expression. Take for example we have a patient with an NCV in the promoter of BRAF. I want to see if the gene is down-regulated as a result of the NCV. Is the correct method to subtract the CT value obtained for GAPDH from the CT value obtained for BRAF in the tested sample ΔCTT(CT tested), and repeat the process for each individual control ΔCTC(CT control). Then Subtract ΔCTC from ΔCTT to obtain ΔΔCt ?

Then using the following equation 2^-ΔΔCt, calculate the expression fold change ? The reason I am unsure if this is the correct method or not because I am not comparing the controls and test samples in a treatment vs no treatment case, I am simply comparing a mutation to healthy control.