if your laboratory is CLIA licensed, as most labs in the US are, you are required to follow the CLIA regulations.
The CFR requires a negative control. It is found in the CLIA regulations 42 CFR 493.1256 Standard: Control Procedures.
42 CFR 493.1256 (c)(2) For each test system, perform control procedures using the number and frequency specified by the manufacturer or established by the laboratory when they meet or exceed the requirements in paragraph (d)(3) of this section.
(d)(3) At least once each day patient specimens are assayed or examined perform the following for -
(i) Each quantitative procedure, include two control materials of different concentrations;
(ii) Each qualitative procedure, include a negative and positive control material.
Further down in that section, there are requirements to test controls before resuming patient testing when a complete change of reagents is introduced... to rotate control material testing among all operators who perform the test, and to test control materials in the same manner as patient specimens.