MAPT and Alzheimer disease: Variation in CSF tau and Aβ42 levels in AD, DOC, and controls may be due to the variability introduced during sample collection and storage like using glass or polystyrene tubes18 than polypropylene tubes, prolonged storage of CSF samples in frozen state or repeated freezing and thawing of CSF, errors introduced due to inadequate study plan like small sample size, less number of controls taken in the study as compared to cases, or case and controls being not age and sex matched [24].