Chronic Screening not paid from chronic benefit

I have been diagnosed with a chronic condition for 2+ years. My specialist Rheumatologist, who is approved by Discovery, as part of my bi annual check up, also sent me for a sonar. The sonar is that with my chronic illness of Lupus / Sjrogens, there is a chance I might develop Lymphoma, this is therefore a precautionary test to catch any further related worsening of this chronic disease. Instead of this being paid through my Chronic benefit, it was taken from my savings. I objected to this & e-mailed Discovery, was phoned by a lady, who I told I was not accepting her explanation, it does not make sense that my chronic cover will not cover a screening procedure to ensure that I am not developing something which i am likely to develop. Please do not send me / explain to me your chronic formulary list. When do we put trust in specialists on YOUR list of doctors, trying to keep us healthy with a Chronic disease. Would Discovery rather I develop Lymphoma & it is only found when it makes me really ill, & then I am hospitalized & we can deal with cancer treatment? What is sensible, R1000 on chronic vs waiting for a R100 000+ cancer claim? Preventative measures or waiting for the worst??