Part B Insider (Multispecialty) Coding Alert

If you're billing for prolonged service codes 99354-99357, you should be careful to avoid adding them to the wrong codes. 

You can't add prolonged service codes to hospital observation (99217-99220), observation or inpatient care (including admission and discharge services) (99234-99236), critical care (99291-99292), or emergency department services (99281-99285), says Tara Conklin, coding specialist at Clark-Holder Clinic in LaGrange, Ga.

Time isn't considered a factor in determining the level of care for those codes, so adding prolonged services codes to them won't win you any favors, Conklin says. Or in the case of critical care, time is already the main factor in reporting the service.

You should code evaluation and management services based on the level of the three components: history, exam, and medical decision-making, then add prolonged services codes for extra time spent with the patient after the initial E/M period has run out. The time spent performing the primary E/M visit doesn't count toward prolonged service codes, Conklin says.

Use 99354 in an outpatient setting and 99356 in an inpatient setting to report the amount of time over half an hour but up to 74 minutes spent with the patient. Then use 99355 (outpatient) or CPT 99357 (inpatient) for each additional half hour, Conklin says. Don't report any time less than 15 minutes beyond the first hour or beyond the final half hour separately.

If time becomes the main factor in setting the level of an E/M service, you should bill the highest level of service along with prolonged services codes. But if time becomes the determining factor but the services last less than 30 minutes past the normal time for the highest level of E/M services, append modifier -21 to the E/M code but don't use prolonged service codes, Conklin says.

You can use 99358 and 99359 to report prolonged services provided without direct face-to-face contact with the patient. You can bill these codes regardless of place of service, and report 99358 for the first half hour over 30 minutes spent with the patient.