Reflex Testing, Standing Orders and Add-Ons: What Genetic Labs Must Document
Short answer: Medicare treats certain reflex tests as implicit in the original order, but testing outside that order's scope ordinarily needs separate authorization from the treating practitioner. A genetic lab's standing orders, reflex rules and add-on workflows must show who authorized what, for which patient, and why. Blanket protocols do not qualify.
Genetic testing workflows are full of "and then also" moments: a panel comes back negative and someone wants deletion/duplication analysis, a result triggers confirmatory sequencing, or a clinician asks for one more gene after the sample is already in the lab. Each of those moments raises the same billing question: did a treating practitioner actually order this? A law-firm analysis published on October 23, 2026 by McGuireWoods, part of its The Lab Protocol series, lays out how standing orders, reflex testing and add-on tests differ and where laboratories get into trouble. This article translates that framework for molecular and genetic labs.
Three terms that get blurred together
McGuireWoods defines a standing order as authorization for specified testing over a defined treatment course or period, typically for recurring monitoring. It stays effective until it expires, is modified or is discontinued. Reflex testing is additional testing triggered by an initial result and considered part of the diagnostic process begun by the original order. An add-on test is testing requested, or deemed necessary, after the original order, and it may need a separate order from the treating practitioner.
The baseline: Medicare still requires an order that shows intent
CMS states on its Lab Test Order Requirements page that the treating physician or practitioner must order laboratory tests, and that "tests you haven't ordered for treating the patient aren't reasonable and necessary." Medical necessity should be documented in the patient's record when the test is ordered, consistent with 42 CFR 410.32. The entity that submits the claim must keep the order for the billed service, documentation of correct order processing and claim submission, and the diagnostic information provided to the lab, including any ICD-10-CM code or narrative description.
CMS lists three acceptable ways to evidence an order for a diagnostic lab test: a signed order or prescription listing the specific test; an unsigned order listing the specific tests performed, with supporting documentation of intent; or an authenticated medical record that supports the provider's intent to order specific tests.
CMS also states that signatures are not required on orders for clinical diagnostic tests paid under the clinical laboratory fee schedule or physician fee schedule. The Noridian Medicare Part B guidance is consistent on this point, while adding that the physician must still document and sign intent in the medical record. In short, the missing signature is rarely the real issue. The missing intent usually is.
Where reflex testing fits
According to McGuireWoods, the Medicare NCCI Policy Manual treats certain reflex tests, such as organism identification after a positive culture or antibody identification after a positive red blood cell antibody screen, as implicit in the original order. Other additional tests require separate authorization. The firm's example is instructive: an order to identify a monoclonal protein band does not automatically authorize testing to determine the protein type.
That example comes from general clinical chemistry, not genetics, but the principle transfers. In our analysis, a genetic lab should ask whether a follow-on method or gene set is genuinely a continuation of the diagnostic question in the original order, or a new question that deserves its own authorization. A requisition that simply says "reflex per lab protocol" without a defined trigger and defined downstream tests invites a reviewer to conclude that nobody with treating responsibility decided anything.
The firm also notes that reflex tests may be separately reportable when the applicable coding and coverage requirements are met. For coding pitfalls with molecular codes, see our guide on CPT 81479 unlisted molecular code denials.
Standing orders: valid, but only if they are specific
McGuireWoods reports that standing orders must show who authorized the testing, what it covers and when it remains in effect, and that blanket protocols applying the same testing to every patient do not qualify. HHS OIG has long recognized standing orders while cautioning laboratories to monitor their continuing validity.
For genetic labs, standing orders are most plausible in recurring monitoring contexts and for repeat submissions from the same practice.
Add-on tests: the highest-risk moment
Add-ons often happen by phone or email after the specimen is already in the lab. CMS says orders may be delivered by a written, signed document, a phone call or email from the provider or office. For phone orders, both the ordering office and the testing facility must document the call in the patient's record. A signed order is not required, but the provider must document intent to order the test. Signature and date stamps are generally not allowed, with a few exceptions.
Noridian adds that telephone or verbal orders must be documented at both locations and signed within the state's required timeframe, that email is acceptable if it can be verified as coming from the physician, and that an electronic requisition is acceptable if it requires a password, with written proof of the process. Noridian also links CERT errors to lack of documentation of physician orders or intent, and notes that tests ordered by a physician who is not treating the beneficiary are not reimbursable.
The practical rule for add-ons: capture the authorization before running the test, not after a payer asks for it. If your front-end team can accept an add-on request verbally, your process should force the same-day documentation CMS describes. Our related piece on Medicare order and signature requirements for genetic testing covers the signature side in more detail.
Pathologist decision points and payer-specific triggers
McGuireWoods cites Medicare LCD L35986, which identifies reflex templates and pre-orders for additional stains before H&E review as potential sources of medically unnecessary testing. Some Medicare contractors and commercial payers require pathologist review of the routine H&E slide before special stains or immunohistochemistry are considered medically necessary. A surgical pathology and cytopathology exception lets a qualifying pathologist perform additional testing not specifically requested when it is needed for a complete and accurate diagnosis, if the exception's other requirements are met.
The lesson for labs that handle tissue-based molecular work is that the sequence of events can itself be a coverage condition. The firm's recommendation is that the laboratory information system "preserve that decision point rather than automate past it." If a payer expects a human review before the next test, an LIS rule that fires the test automatically can create the very exposure you are trying to avoid.
A four-question protocol review
McGuireWoods recommends asking four questions of every reflex or add-on protocol: Does the initial order cover additional testing, or is separate authorization required? What finding triggers the next test, and must someone review it first? Do coverage policies impose a different trigger or sequence? Can the lab reconstruct why the test was performed and who authorized it?
We would add one operational step: run these questions against your actual claims, not just your written policy. Pull a sample of recent reflex and add-on claims and confirm that each has an authorization trail matching what CMS describes. Where it does not, fix the process before an auditor finds the gap. Labs that also see duplicate-test edits should review our guide to modifier 91 and duplicate lab test denials.
What this means for your lab
Three actions are worth taking this quarter. First, inventory every reflex rule and standing order in your LIS and requisition templates, and record the trigger, downstream tests, authorizing party and expiry for each. Second, write down your add-on intake procedure so that a phone or email request is documented at both ends the same day. Third, schedule a recurring review against payer policy changes. State law and individual payer rules may add conditions beyond Medicare's, as McGuireWoods notes, so Medicare compliance is a floor, not a ceiling.
ScreenMyGene helps labs and ordering clinicians structure test selection and documentation upstream of the claim. To see how, visit the ScreenMyGene homepage, or read our overview of why genetic testing claims get denied.
Frequently asked questions
Does Medicare require a signed requisition for every genetic lab test?
No. CMS states signatures are not required on orders for clinical diagnostic tests paid under the clinical laboratory fee schedule. However, the medical record must still show the practitioner's intent to order the service and support medical necessity for that patient. Payer and state rules may add requirements.
What is the difference between reflex testing and an add-on test?
Reflex testing is triggered by an initial result and is considered part of the diagnostic process started by the original order. An add-on is requested or deemed necessary after the original order and may need a separate order from the treating practitioner. Scope of the original order decides which applies.
Can a lab use a blanket reflex protocol for all patients?
McGuireWoods states that blanket protocols applying the same testing to every patient do not qualify as standing orders. Standing orders must show who authorized the testing, what it covers and when it remains in effect. Protocols should also be reviewed periodically against clinical practice and payer policy.
How should a lab document a phone order for an add-on test?
CMS says both the ordering office and the testing facility must document the call in the patient's record. A signed order is not required, but the provider must document intent to order the test. Noridian adds that verbal orders should be signed within the state's required timeframe.
Why does the order of testing matter for payment?
Some payers and Medicare contractors require a review step before follow-on testing is considered medically necessary, such as pathologist review of the H&E slide before special stains under LCD L35986. Automating past that step can produce testing a payer deems unnecessary.
Educational disclaimer: This article is for general educational and informational purposes for laboratories, medical directors and revenue cycle teams. It is not legal, billing, coding, clinical or compliance advice, and it does not replace guidance from your compliance counsel, Medicare Administrative Contractor or payers. Coverage and documentation rules change; verify against current official sources.
Sources: McGuireWoods, "The Doctor Ordered What? Standing Orders, Reflex Testing and Add-On Tests," The Lab Protocol, Oct. 23, 2026; CMS, Lab Test Order Requirements (cms.gov/lab-test-order-requirements); Noridian Medicare JF Part B, Physician's Orders for Diagnostic Laboratory Tests; 42 CFR 410.32 as cited by CMS and Noridian; Medicare Benefit Policy Manual, Ch. 15, 80.6.1 as cited by Noridian.