Crystal's MCW Coder HubModifier -QX: Qualified Nonphysician Anesthetist Medically Directed
Short Definition
The CRNA or anesthesiologist assistant (AA) provided anesthesia services under the medical direction of a physician anesthesiologist.
Long Definition
Modifier QX is a HCPCS Level II anesthesia payment modifier reported by a CRNA or anesthesiologist assistant (AA) to indicate they provided anesthesia services while under the medical direction of a physician anesthesiologist. This is the CRNA/AA side of the paired billing scenario — the anesthesiologist simultaneously reports modifier QK (if directing 2-4 cases) or QY (if directing 1 case) on their own separate claim.
Modifier QX is specifically the nonphysician provider’s claim indicator. It tells the payer that the CRNA or AA did not work independently — their anesthesia service was provided under physician oversight meeting CMS medical direction standards.
Both the anesthesiologist (billing QK or QY) and the CRNA/AA (billing QX) each receive 50% of the applicable allowable, making the combined reimbursement equivalent to the payment that would have been made if a single provider performed the case under modifier AA.
Who Reports Modifier QX
- CRNA (Certified Registered Nurse Anesthetist) — reports QX when medically directed by a physician.
- Anesthesiologist Assistant (AA) — also reports QX when medically directed by a physician.
- Physician anesthesiologists do NOT report QX — they report QK or QY for their side of the directed case.
When to Use
- The CRNA or AA performed the anesthesia service while under the medical direction of a supervising physician anesthesiologist.
- The supervising physician met all seven CMS conditions for valid medical direction.
- The supervising physician is billing QK (if directing 2-4 concurrent cases) or QY (if directing only this one case).
- Both the CRNA/AA and the physician submit separate claims for the same anesthesia service on the same date of service.
When NOT to Use
- When the CRNA provided anesthesia without any physician medical direction — use QZ instead.
- When the physician is medically supervising (not directing) — the CRNA may still report QX but the physician reports AD; reimbursement structure changes significantly.
- Never report QX on the same claim line as AA, QK, QY, QZ, or AD — these are mutually exclusive.
- When the CRNA is being directed by another CRNA (teaching CRNA scenario) — specific rules apply; verify payer guidance.
Reimbursement
- CRNA/AA bills QX: 50% of the applicable CRNA fee schedule allowable.
- Physician bills QK or QY: 50% of the physician anesthesia fee schedule allowable.
- Each provider submits their own claim, under their own NPI, for the same anesthesia service.
Anesthesia Payment Modifier Family — Quick Reference
| Modifier | Reported By | Scenario | Rate |
|---|---|---|---|
| -AA | Anesthesiologist | Personally performed, full case | 100% |
| -QK | Anesthesiologist | Medically directing 2-4 concurrent cases | 50% |
| -QY | Anesthesiologist | Medically directing 1 CRNA | 50% |
| -AD | Anesthesiologist | Supervising 5+ concurrent cases | Limited base units only |
| -QX | CRNA / AA | Medically directed by a physician | 50% |
| -QZ | CRNA | Without medical direction by a physician | 100% CRNA rate |
Quick Example
- Anesthesiologist Dr. C is medically directing two concurrent OR cases.
- CRNA A is performing the anesthesia for a laparoscopic cholecystectomy (01652).
- CRNA A bills: 01652-QX under their own NPI — receives 50% of the CRNA allowable.
- Dr. C bills: 01652-QK under their own NPI for the same case — receives 50% of the physician allowable.
- Documentation confirms Dr. C met all seven CMS medical direction conditions for both concurrent cases.