20 C.F.R. § 10.321

(a) If one medical opinion holds more probative value, OWCP will base its determination of entitlement on that medical conclusion (see § 10.502). A difference in medical opinion sufficient to be considered a conflict occurs when two reports of virtually equal weight and rationale reach opposing conclusions (see James P. Roberts, 31 ECAB 1010 (1980)).

(b) If a conflict exists between the medical opinion of the employee's physician and the medical opinion of either a second opinion physician or an OWCP medical adviser or consultant, OWCP shall appoint a third physician to make an examination (see § 10.502). This is called a referee or impartial examination. OWCP will select a physician who is qualified in the appropriate specialty and who has had no prior connection with the case. The employee is not entitled to have anyone present at the examination unless OWCP decides that exceptional circumstances exist. For example, where a hearing-impaired employee needs an interpreter, the presence of an interpreter would be allowed. Also, a case file may be sent for referee or impartial medical review where there is no need for an actual examination, or where the employee is deceased.