When Diagnostic Tests Are and Aren’t Covered by Payers

The idiom “a needle in a haystack” refers to something extremely difficult to find. It implies that the needle is inherently valuable. We celebrate the searcher who finds the prize, assuming discovery is the victory. But finding the needle is of limited value without the thread, fabric, or skill to use it.

In modern diagnostics, the “needle” is a biomarker, a genetic variant, or a specific anatomic or physiological finding. While technology is increasingly proficient at detection, payers ask a different question: What happens once the needle is found? A test may excel at detecting or excluding disease, but clinical validity alone (sensitivity and specificity) is rarely enough to warrant coverage. Coverage depends on proven clinical utility — that evidence exists to support changes in patient management. For diagnostics competing with less-expensive alternatives, payers often require economic utility — proof that clinical benefits justify the incremental cost.

In practice, diagnostics fall into six recurring patterns:

1. Generally not covered — informational only

These diagnostics provide data without a clear management “thread” — they do not alter treatment, monitoring, or counseling. For coverage, these tests must fulfill a role within an existing standard of care or wait for an intervention that requires the test result for patient selection.

• Multi-cancer early detection (MCED) blood tests: While these “liquid biopsies” detect circulating tumor DNA across dozens of cancers, they are not yet FDA-approved and lack validated management pathways. Because trials have not yet proven improved survival, the National Comprehensive Cancer Network (NCCN) limits use to research, and payers universally deny coverage.
• Immunoglobulin G (IgG) food sensitivity testing: Despite commercial popularity, major allergy societies recommend against this testing as it measures normal immune exposure rather than pathology. Payers deny coverage because the lack of proven outcome benefits renders the results as clinically unactionable.
• Microbiome sequencing and wellness panels: While these generate detailed profiles of gut flora or nutritional status, they lack established clinical utility in evidence-based guidelines. Payers categorize them as lifestyle curiosities rather than medical necessities and routinely deny reimbursement.

2. Generally not covered — less mature evidence

These tests show promise, but the lag between technical readiness and outcomes data keeps them in the “investigational” category. Coverage for these tests should begin to take root when high-quality clinical utility studies supporting their use are published in peer-reviewed journals.

• Alzheimer’s blood biomarkers (Aβ42/40 and p-tau): These markers have revolutionized classification in specialty clinics, yet major organizations (American Academy of Neurology, National Institute on Aging) do not yet recommend them for routine clinical practice. Payers often deny coverage, citing a lack of prospective data showing improved outcomes. However, in 2025, the Alzheimer’s Association released its first clinical practice guideline, specifically supporting high-performance blood tests (like p-tau217) as a triage tool to rule out pathology in symptomatic patients within specialty settings. This new support suggests a path to future coverage.
• Circulating tumor DNA (ctDNA) minimal residual disease (MRD) for solid tumors: MRD technology can detect molecular recurrence months before imaging, but the NCCN still lists it as investigational for most solid tumors. The test remains largely unreimbursed because there is no consensus on whether results should trigger a change in treatment.
• Liquid biopsy early detection panels: These identify ctDNA in asymptomatic individuals to replace or augment existing screening. Payers deny coverage, labeling them “less mature” because high sensitivity has not yet translated into prospective evidence that blood-based discovery improves survival compared with gold standards like mammography or colonoscopy.

3. Broadly covered — new treatments support use

These diagnostics achieve coverage after new clinical interventions — targeted therapies, surgical protocols, or preventive pathways — make a test result a prerequisite for action.

• HER2 testing in breast cancer: HER2 testing achieved broad coverage only after the 1998 approval of trastuzumab, which demonstrated a survival benefit and made the diagnostic a prerequisite for therapy.
• Fractional flow reserve (FFR): FFR technology achieved broad reimbursement only when new clinical protocols required it to justify percutaneous coronary intervention (PCI). It became the standard of care after the FAME trial (2009) proved it led to better survival and lower costs, unlocking payer support.
• EGFR mutation testing: This test rapidly achieved broad coverage because results became a mandatory prerequisite for targeted tyrosine kinase inhibitors (TKIs). The test became a prerequisite for reimbursement once FDA labels for TKIs like gefitinib (2003) and erlotinib (2004) mandated targeted testing.

4. Broadly covered — new evidence supports use

Coverage for these tests was granted after prospective trial data demonstrated that the results helped improve outcomes, avoided unnecessary treatment, or reduced harm. Evidence — not just new molecule launches — generated evidence-based guideline support. While evidence-based guidelines often facilitate coverage, they are not a prerequisite; payers frequently reimburse a new standard of care based on the strength of evidence alone, often preceding formal guideline updates.

• Oncotype DX recurrence score: Initially subject to inconsistent reimbursement, this assay attained broad coverage after the TAILORx (2018) and RxPONDER (2020) trials proved that patients could safely avoid chemotherapy.
• Expanded BRCA testing: In the 2010s, evidence that results guided life-saving prophylactic surgeries expanded coverage beyond restrictive family-history criteria. Data showing a 90% reduction in cancer incidence established the test as a broadly covered medical necessity.
• DPYD pharmacogenomic testing: Reimbursement expanded after prospective studies (2015–2018) showed that genotype-guided dosing significantly reduced toxicity, moving the test from a precautionary measure to a covered standard.

5. Reimbursed on entry — self-evident clinical utility

These diagnostics were covered upon entry because they addressed clear clinical needs where the next step was logical. They became a broadly recognized standard of care based on clinical utility.

• Cardiac troponin: Introduced in the mid-1990s, troponin provided a self-evident improvement over existing methods for triaging chest pain. Because results guided the decision to admit for acute coronary syndrome, it was reimbursed almost immediately.
• HbA1c testing: The utility of HbA1c in adjusting diabetes therapy was apparent from its introduction. HbA1c was broadly covered as a standard of care well before the publication of formal evidence-based guidelines.
• Rapid infectious disease assays (flu, strep, RSV): These were reimbursed on entry because results trigger immediate, universally accepted actions — such as antiviral or antibiotic treatment, and return-to-work or school decisions — allowing rapid paths to care while bypassing lengthy evidence-generation hurdles. COVID-19 testing ultimately reflected the same logic, but coverage and payment were driven by emergency federal mandates and public financing rather than conventional payer reimbursement decisions.

6. Variable coverage — actionable but contested

While these diagnostics influence clinical decisions, coverage is inconsistent because payers question their superior clinical utility or incremental value over lower-cost traditional standards. For tests with variable coverage — actionable but contested, data directly linking test results to management changes that improve outcomes will encourage wider coverage. For those diagnostics that compete with cheaper, existing alternatives, it may also be necessary to provide rigorous health economic assessments that justify the cost.

• Comprehensive tumor genomic profiling (next-generation sequencing panels): While Medicare covers broad panels for advanced cancer, commercial payers often limit coverage to smaller, targeted panels for early-stage cancer where fewer genomic results are actionable.
• Pharmacogenomic panels for antidepressant selection: These panels use genetic profiles to guide medication use for major depressive disorder. However, despite trial data showing improved remission (GUIDED, 2019), many commercial payers deny coverage, citing a lack of evidence that these panels provide superior outcomes compared with empiric prescribing.
• Coronary artery calcium (CAC) scoring: This highly actionable test can determine if a patient starts a lifetime of statin therapy. However, many payers deny coverage based on its classification as a screening tool, questioning whether its additional diagnostic value justifies the population-level cost.

Moving toward coverage

A diagnostic’s reimbursement status is dynamic, moving from “interesting” to “indicated” as data mature and new interventions emerge. To move toward coverage, developers must address the limiting factor for their category — waiting for an intervention, generating evidence of clinical utility, or justifying incremental cost.

As medical costs continue to rise, payers are likely to apply this logic more stringently. Expensive diagnostics will face higher evidentiary thresholds, particularly when they compete with lower-cost alternatives or expand testing into broader populations. Tests supported by weaker or indirect evidence may struggle not only to achieve coverage but to maintain it as utilization grows and their budget impact becomes visible.

In the end, diagnostics are not rewarded for finding ever-smaller needles. Coverage follows only when the thread is strong enough to stitch discovery into evidence-based care.