You do not have to wait.
(emphasis mine)
According to Official Guidelines, Section IV, L
For outpatient encounters for diagnostic tests that have been interpreted by a physician, and the final report is available at the time of coding, code any confirmed or definitive diagnosis(es) documented in the interpretation. Do not code related signs and symptoms as additional diagnoses.
According to CMS, Claims Processing Manual, Chapter 23, Section 10.1.2
D. If the individual responsible for reporting the codes for the testing facility or the
physician's office does not have the report of the physician interpretation at the time of
billing, the individual responsible for reporting the codes for the testing facility or the
physician's office should code what they know at the time of billing. Sometimes reports of
the physician's interpretation of diagnostic tests may not be available until several days
later, which could result in delay of billing. Therefore, in such instances, the individual
responsible for reporting the codes for the testing facility or the physician's office should
code based on the information/reports available to them, or what they know, at the time of
billing.