Yes. Employers are required to maintain records sent to them by the MRO. MRO reporting requirements for drug test results are found at 49 CFR 40.163. Pursuant to 49 CFR 382.401, employers must maintain certain drug and alcohol testing records for five (5) years, including positive drug test results. Employers may maintain these records electronically as long as the records can be produced for inspection pursuant to 49 CFR 390.31.