Thank you for posting your query at DoctorSpring.com
I understand your concern.
ABI test is done to exclude arterial occlusive diseases.
DVT is Deep Vein Thrombosis. This is related to vein.
It doesn't affect ABI test.
But,the best investigation is Colour doppler of the left lower limb.
Redness is not characteristic feature of DVT.
Swelling and pain will be present.The same features can be seen in Cellulitis.
If you are suspecting DVT, vein has to be examined. By colour doppler, both arterial system and venous system can be seen.
So i will advise you get a colour doppler done and upload the reports for me to be able to guide you further.
Feel free to discuss further,
Wish you good health.