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Modifier 91

CPT numeric modifiers (AMA · CPT Appendix A)

Modifier 91. Repeat Clinical Diagnostic Laboratory Test — medically necessary repeat of the same lab test, same day, for serial values. Not for re-running an abnormal result.

Reference only — CPT descriptors are AMA-copyrighted (paraphrased). Payment percentages and acceptance vary by payer; verify against the current CPT/HCPCS files and payer policy.

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