Modifier QK: Medical Direction of 2–4 Anesthesia Cases
QK bills an anesthesiologist medically directing two to four concurrent cases, paid 50% of the personally performed rate. The seven rules, ratios and QK vs QY.
Modifier QK is a HCPCS Level II anesthesia modifier that CMS defines as "Medical direction of two, three or four concurrent anesthesia procedures involving qualified individuals" (Pub. 100-04, ch. 12, §50.I). The anesthesiologist bills each directed case with QK and is paid 50% of the allowance for the same case personally performed; the directed CRNA or anesthesiologist assistant bills QX for the other 50%.
Key takeaways
- QK covers a 1:2, 1:3 or 1:4 ratio of anesthesiologist to concurrent cases. One directed case uses QY; more than four is medical supervision, AD.
- The anesthesiologist must perform all seven medical-direction steps in §50.C for every case, and document them.
- Medicare pays 50% of the personally performed allowance to the anesthesiologist and 50% to the CRNA or AA.
- Concurrency counts every overlapping case, including non-Medicare patients.
- QK is a payment modifier. Informational modifiers such as QS for monitored anesthesia care are reported with it, not instead of it.
Modifier QK · payment effect
With and without the modifier
01402 without QK · national facility
$0.00
01402-QK · No change to the rate
$0.00
Anesthesia medical direction of 2–4 concurrent cases. Anesthesia is paid outside the physician fee schedule RVUs (each directed case at 50%).
When to use the QK modifier
Use QK on each case when the anesthesiologist medically directs two, three or four concurrent cases involving qualified individuals (CRNAs, anesthesiologist assistants, interns or residents, in any combination), and for each case personally:
- Performs the pre-anesthetic examination and evaluation.
- Prescribes the anesthesia plan.
- Participates in the most demanding procedures in the plan, including induction and emergence where applicable.
- Ensures any procedures they don't perform are performed by a qualified individual.
- Monitors the course of anesthesia at frequent intervals.
- Remains physically present and available for immediate diagnosis and treatment of emergencies.
- Provides indicated post-anesthesia care.
The record must show the pre-anesthetic evaluation, the post-anesthesia care, presence during some of the monitoring, and presence at the most demanding parts of the plan, including induction and emergence where indicated (§50.C). In a group, one anesthesiologist may do the pre-anesthesia evaluation and another the rest, as long as the record names who did what.
Concurrency. Count the maximum number of overlapping cases the anesthesiologist is directing during each case, Medicare or not. Three overlapping rooms, two with commercial patients, are still 1:3 and the Medicare case is QK.
Brief interruptions don't break medical direction: a short emergency nearby, placing a labor epidural, periodic obstetric monitoring, receiving the next patient, checking or discharging recovery-room patients, or handling scheduling (§50.C).
When not to use the QK modifier
- One case with a CRNA or AA. Use QY (anesthesiologist) and QX (CRNA).
- The anesthesiologist performed the case alone. Use AA.
- A CRNA worked without medical direction. The CRNA bills QZ.
- Teaching cases with residents that meet the teaching physician rules in §50.B are paid at the personally performed rate, not QK.
How the QK modifier affects payment
Anesthesia is paid as (base units + time units) × the locality's anesthesia conversion factor. Time units are anesthesia minutes divided by 15, rounded to one decimal place (§50.G). Medical direction splits that allowance:
The physician's 50% comes from §50.C and 42 CFR 414.46(d)(3); the CRNA's medically directed allowance is set by the same percentage under 42 CFR 414.60. The directing physician ordinarily reports the same anesthesia time as the CRNA.
QK vs QY, QX, QZ, AA and AD
| Modifier | Who bills | Situation | Payment basis |
|---|---|---|---|
| AA | Anesthesiologist | Personally performed | Full allowance |
| QK | Anesthesiologist | Directing 2–4 concurrent cases | 50% |
| QY | Anesthesiologist | Directing one CRNA or AA | 50% |
| QX | CRNA or AA | Medically directed | 50% |
| QZ | CRNA | No medical direction | Full allowance |
| AD | Anesthesiologist | Supervising more than four cases | 3 base units (+1 time unit if present at induction) |
FAQ
What is the QK modifier?
A HCPCS anesthesia payment modifier meaning the anesthesiologist medically directed two, three or four concurrent anesthesia cases involving CRNAs, anesthesiologist assistants, interns or residents.
How much does Medicare pay with QK?
50% of the allowance the anesthesiologist would get for personally performing the case. The CRNA or AA billing QX for the same case is allowed the other 50%.
What is the difference between QK and QY?
QK is for directing two to four concurrent cases. QY is for directing a single CRNA or AA in one case. Both pay the anesthesiologist 50%.
What happens if an anesthesiologist directs five cases?
The cases are no longer medically directed. They are medically supervised and billed with AD, which Medicare pays at three base units per procedure, plus one time unit if the anesthesiologist documents presence at induction.
Can QK be used with QS for monitored anesthesia care?
Yes. QS is informational; CMS requires the actual anesthesia time and one payment modifier, such as QK, on the claim.
Keep reading
- Modifier 80 and AS for assistants at surgery.
- Modifier 51 for multiple procedures.
- Codes on this page: 01402 00790 27447
Sources: CMS Medicare Claims Processing Manual, Pub. 100-04, ch. 12, §§50 and 140.3–140.4; 42 CFR 414.46(d) and 414.60(a). Verified October 6, 2026.
