Day 29 of ALS Awareness Month: ALS is a “differential diagnosis,” i.e. the MD rules out EVERYTHING else, and then says it’s ALS.
(Using male pronouns because our doc happens to be male.) When a neurologist is trying to diagnose from symptoms, he begins asking questions from a decision tree in his head. No memory problems? Rule out Alzheimer’s. Haven’t lost sensation in any part of the body? Rule out neuropathy. etc etc. What’s left is ALS. This is why it can take so long to diagnose ALS. The neurologist has to actually see progression to make a tentative diagnosis of ALS. What we need is one or more biomarkers to diagnose the disease.
BIOMARKERS! In cancer, you can biopsy the tumor and see the state of the malignant cells. In diabetes, you can take a urine sample and see how much sugar is in it. In ALS, we got nothin’. The advantage of biomarkers is not just for diagnosis, but for treatment. (e.g. In diabetes, if a treatment is working, the blood sugar level in the urine goes down.) We don’t have biomarkers to measure the progress of ALS or to determine if an intervention is helping treat the disease. What do we have? We have (1) a subjective questionnaire we fill out to measure the pALS’ daily functions, and (2) we can track how long s/he survives. And also … no, that’s basically it. We also measure declining strength and lessened lung capacity, but none of these is a biomarker for the disease. We have no blood test, no biopsy, no urine sample. The absence of biomarkers is what makes finding an effective treatment SO HARD!