Genetic Panels for Immunodeficiency: Costly Testing Traps

But choosing a test is not simply a matter of ordering the largest available panel. The decision sits at the intersection of clinical presentation, laboratory phenotype, sequencing technology, insurance policy, and the family’s ability to manage an uncertain result.

That distinction matters because the diagnostic landscape is broader than many families realize. More than 450 distinct genetic conditions are now recognized within the spectrum of inborn errors of immunity, formerly grouped under the broader term primary immunodeficiency. A targeted primary immunodeficiency genetic panel may be highly appropriate for one child and a poor first step for another. In selected cases, whole exome sequencing for immunodeficiency can produce a diagnosis more efficiently—and at a lower overall cost—than ordering a panel first and escalating only after the panel is negative.

The right question is therefore not, “Which test is most comprehensive?” It is: Which testing strategy best matches this child’s immune phenotype, the likely mechanism of disease, and the consequences of a result?

The financial reality of diagnostic sequencing

The pediatric genetic testing cost is often discussed as though it were a fixed price. In practice, the price on a laboratory estimate is only one part of the financial picture. Families may also face consultation fees, repeat blood draws, confirmatory testing, parental testing, genetic counseling, travel to a specialist center, and follow-up investigations after a result that changes clinical care.

A standard primary immunodeficiency panel typically costs around $1,500 when paid out of pocket. Whole exome sequencing or whole genome sequencing may range from $4,000 to $12,000. These figures are broad, and the amount a family ultimately pays depends on the laboratory, the health plan, the indication, whether testing is performed as a trio with both parents, and how the claim is processed.

The least expensive test at the beginning is not always the least expensive diagnostic pathway.

A targeted panel may contain dozens or hundreds of genes selected because they are known to cause immune disorders. This can be an efficient approach when the clinical presentation is tightly defined. For example, a child with a consistent pattern of severe viral infections, characteristic cytopenias, abnormal lymphocyte subsets, and a family history suggestive of X-linked disease may benefit from a focused analysis directed toward a particular disease group or gene set.

However, a panel can become costly when it is used as the first step in a child whose phenotype is broad or evolving. If the panel is negative, the next step may be another panel, deletion and duplication analysis, single-gene testing, parental studies, or whole exome sequencing. Each additional test brings another authorization process and another opportunity for an ambiguous result.

The practical comparison looks like this:

The longitudinal study behind the final row followed 878 patients with suspected primary immunodeficiency between 2010 and 2020. A WES-only diagnostic pipeline produced a diagnosis in 45% of patients and saved an estimated $300 to $950 per patient compared with a targeted panel followed by WES. That finding does not mean WES should replace every panel. It does show why a reflexive “panel first, broader testing later” approach can be inefficient when the initial clinical picture is not narrow.

The cheapest first test is not necessarily the cheapest route to a diagnosis; sequencing strategy should be designed around the probability of changing care.

Diagnostic yield: what a negative panel can and cannot tell us

Diagnostic yield is the proportion of tested patients who receive a result considered explanatory for their clinical condition. For next-generation sequencing in primary immunodeficiencies, the average diagnostic yield is approximately 29%, with reported studies ranging from 10% to 79%. For whole exome sequencing, the average is about 38%, with reported ranges from 15% to 70%.

These ranges are wide because “suspected immunodeficiency” is not one clinical group. Yield is influenced by the strength of the phenotype, the patient’s age, the laboratory findings, the presence of syndromic features, the number of genes analyzed, the quality of variant interpretation, and whether the family’s genetic structure allows parental comparison.

A child with a clear immune phenotype and a strong family history is not equivalent to a child being tested after recurrent respiratory infections alone. Recurrent infections are common in childhood, particularly in the setting of daycare exposure, asthma, anatomic airway disease, or inadequate vaccination responses for reasons unrelated to a monogenic immune disorder. The pre-test probability changes the value of sequencing.

Before choosing between panel and exome, we usually want the clinical presentation translated into a structured phenotype:

• Infection pattern: bacterial, viral, fungal, or opportunistic infections; their severity; the anatomical sites involved; and whether infections are unusually persistent or difficult to treat.
• Age at onset: infections beginning in the first months of life carry a different diagnostic weight from recurrent uncomplicated infections beginning after school entry.
• Laboratory phenotype: complete blood count trends, immunoglobulin concentrations, vaccine antibody responses, lymphocyte subsets, neutrophil function, complement studies, and inflammatory markers when clinically indicated.
• Non-immune findings: eczema, enteropathy, autoimmunity, cytopenias, growth concerns, skeletal findings, neurologic features, or endocrine disease may point toward a syndromic disorder.
• Family structure: consanguinity, affected relatives, unexplained infant deaths, recurrent pregnancy loss, and sex-specific inheritance patterns can materially influence test selection.
• Treatment history: response to immunoglobulin replacement, antimicrobial prophylaxis, vaccination, or hematopoietic stem cell transplantation may refine the phenotype but does not, by itself, establish a genetic diagnosis.

A negative result must then be interpreted in that context. A negative targeted panel does not rule out a primary immunodeficiency. The panel may not contain the relevant gene, may not detect a particular class of variant, or may have technical limitations in a difficult genomic region. Some immune disorders remain genetically unresolved even after broad sequencing.

This is why a negative test should be treated as one result within the diagnostic pathway—not as a verdict that the child’s immune system is normal.

The opposite problem is also common: a test may identify a gene variant, but the variant may not explain the child’s illness. The presence of a molecular finding can create a false sense of closure, particularly when the clinical phenotype is nonspecific. A result becomes clinically meaningful when the gene, variant, inheritance pattern, functional evidence, and patient presentation align.

The technical limitations hidden inside a “comprehensive” panel

The word “panel” can sound reassuringly complete. Yet panel design is not only about the number of genes listed on a laboratory website. It is also about whether the assay can reliably read the relevant parts of those genes and detect the type of change responsible for disease.

Most routine next-generation sequencing approaches perform well for many single-nucleotide variants and small insertions or deletions in coding regions. They are less uniformly effective for large deletions, duplications, deep intronic variants, regulatory variants, repeat expansions, complex rearrangements, and regions with high sequence similarity to pseudogenes. Some laboratories add copy-number analysis or other methods, while others require separate testing.

IKBKG is a clinically important example. The gene, associated with NEMO deficiency, has 99% homology with the non-pathogenic pseudogene IKBKGP1. That similarity can interfere with standard sequencing and variant interpretation. A routine panel may not be sufficient to characterize the region without specialized methods, which may include confirmatory Sanger sequencing or long-read approaches depending on the suspected variant and laboratory capability.

The lesson is not that panels are unreliable. It is that the test report should be read at the level of method and coverage, not just the gene list.

When reviewing a proposed assay, we should ask:

• Does the laboratory include deletion and duplication analysis?
• Are mitochondrial genes, copy-number changes, or structural variants assessed?
• Are difficult genes or pseudogene-associated regions addressed with a specialized method?
• What is the laboratory’s coverage threshold for the relevant genes?
• Can the laboratory perform parental testing if a potentially important variant is identified?
• How are newly recognized disease genes handled after the original report?
• Does the laboratory offer periodic reanalysis of negative exome data?

These questions are particularly relevant when the clinical presentation is strongly suggestive but the first test is negative. A child may have a genuine immune disorder even when the initial assay did not capture the mechanism.

In some cases, the most useful next step is not immediately ordering a broader test. It may be a laboratory review of the original data, a targeted assay using a different technology, or a return to the immune phenotype to determine whether the suspected diagnosis still fits. Genetic testing should remain connected to clinical immunology rather than operating as an isolated laboratory exercise.

The VUS dilemma: when a genetic finding is not a diagnosis

Variants of uncertain significance, or VUS, are one of the most important genetic testing insurance coverage pitfalls and clinical interpretation traps. A VUS means that available evidence is insufficient to classify the variant as either benign or disease-causing. It is not a molecular diagnosis.

This distinction can be difficult for families because a laboratory report may identify a specific change in a gene that has a known relationship to immune disease. But the gene-disease relationship and the individual variant are separate questions. A variant may be located in a relevant gene while lacking enough evidence to explain the child’s presentation.

A VUS can lead to:

1. Diagnostic confusion. The family may believe the cause has been found even though the laboratory has not established pathogenicity.

2. Unnecessary testing. Clinicians may order repeated imaging, functional studies, or family testing without a clear plan for how the information will alter management.

3. Inappropriate treatment. A child may be exposed to immunosuppression, antimicrobial prophylaxis, immunoglobulin replacement, or other interventions based primarily on an uncertain genetic finding rather than the complete clinical picture.

4. Misclassification within the family. Relatives may be labeled as affected or at risk when the significance of the variant remains unresolved.

5. Emotional and practical strain. Families may reorganize care, schooling, or future reproductive decisions around information that could later be reclassified.

The correct response is disciplined interpretation. We should ask whether the variant is consistent with the inheritance pattern, whether it is present in an unaffected relative, whether the child’s phenotype matches the established disease spectrum, and whether functional evidence supports a damaging effect. A variant should not be used to direct major clinical decisions solely because it appears on a report.

This is where genetic counseling becomes part of clinical care rather than an optional add-on. Families need a clear explanation of what the result does and does not establish, how often laboratories may update classifications, and which clinical findings should continue to guide treatment.

A VUS is a prompt for careful follow-up, not permission to replace phenotype-based care with a molecular label.

The management pathway should therefore remain anchored to observed immune dysfunction. If a child has documented absent or profoundly reduced T-cell function, that finding may require urgent management regardless of whether sequencing identifies a pathogenic variant. Conversely, a VUS in an immune-related gene should not override normal immunological studies and an inconsistent clinical presentation.

Choosing between a panel and whole exome sequencing

There is no universal first-line test for every suspected inborn error of immunity. We can, however, identify situations in which one strategy is more likely to provide useful information.

A targeted panel may be reasonable when:

• the phenotype is well defined and maps closely to a known group of disorders;
• initial immunological studies strongly narrow the differential diagnosis;
• a particular inheritance pattern is apparent;
• rapid testing of a limited set of genes is clinically important;
• the laboratory has strong technical coverage for the genes under consideration;
• the clinical team has a clear plan for what will happen after a negative result.

Whole exome sequencing may be more informative when:

• the child has a broad or atypical immune phenotype;
• multiple organ systems are involved;
• the differential diagnosis includes both immune and non-immune syndromic conditions;
• previous targeted testing was negative;
• the family history is uninformative or unavailable;
• the suspected condition could be caused by one of many genes;
• the team wants to avoid a long sequence of overlapping tests.

A trio exome, involving the child and both biological parents, can sometimes improve interpretation by showing whether a variant is inherited, new in the child, or present in a pattern compatible with recessive disease. The availability and cost of trio testing vary, and a trio result still requires clinical correlation.

Whole genome sequencing can theoretically assess more genomic territory than exome sequencing, but the long-term cost-effectiveness of using WGS as a first-line test in pediatric cohorts remains uncertain. A broader assay does not automatically solve every technical problem, and a wider data set may increase the number of findings that require interpretation.

In real clinical practice, the decision is often made through collaboration between the pediatric immunologist, genetic counselor, clinical geneticist, and laboratory. The laboratory’s technical strengths matter as much as the marketing description of the test. Two panels with similar gene counts may differ substantially in coverage, copy-number detection, variant classification, and reanalysis policy.

Insurance denials and the access problem

Insurance approval is often treated as an administrative detail, but it can determine whether a child receives a timely diagnosis. Pediatric genetic testing requests face an insurance denial rate of approximately 18.3%, with genetic testing denied more frequently than other clinical tests. The exact denial rate specifically for primary immunodeficiency testing is not established, but the broader pattern is clinically relevant.

A denial does not necessarily mean the test lacks medical value. It may reflect the insurer’s criteria, incomplete documentation, the selected billing code, a requirement for prior authorization, or a mismatch between the laboratory’s request and the policy language.

A strong authorization package should connect the test to the child’s clinical presentation rather than simply listing recurrent infections. Documentation may include:

• the infection history, including severity, unusual organisms, hospitalizations, and treatment response;
• objective immune abnormalities and their persistence over time;
• relevant family history;
• non-immune features that raise concern for a syndromic disorder;
• prior diagnostic testing and why it has not resolved the question;
• the specific management decision that could change if a pathogenic result is found;
• the limitations of the proposed test and the reason it is preferable to a narrower or sequential strategy.

We should also distinguish between prior authorization and coverage. Authorization does not guarantee that the claim will be paid, and a denial after testing can still leave the family with a substantial bill. Before a sample is collected, ask the laboratory for an estimate of the patient responsibility and confirm whether the laboratory has a financial assistance policy, a self-pay rate, or a process for appealing a denial.

If insurance refuses coverage, the next steps usually involve obtaining the written reason for denial, reviewing the policy criteria, submitting additional clinical documentation, and requesting an appeal from the treating specialist. The appeal is stronger when it explains not only why sequencing is medically indicated, but also why the proposed test is an efficient part of the diagnostic pathway.

Some families may also qualify for research-based or foundation-supported testing. The Jeffrey Modell Foundation’s Jeffrey’s Insights program, launched as a pilot in January 2019 and expanded globally in 2020, offers free genetic sequencing through participating network centers for patients with suspected primary immunodeficiency. Eligibility, availability, and the scope of testing depend on the participating center, so families should discuss referral options with their immunology team rather than assuming access is automatic.

Research testing can be valuable, but it should be understood clearly. A research result may not carry the same validation, reporting process, or clinical follow-up obligations as a test ordered through a clinical laboratory. The care team should explain whether results will be returned, which findings are actionable, and how the information will be incorporated into medical records and future care.

Building a diagnostic route that remains useful after the report arrives

The most successful genetic testing pathway begins before the blood draw and continues after the report. The test is only one component of a larger diagnostic process that includes immune phenotyping, treatment decisions, family counseling, and periodic reassessment.

For families and clinicians, the following sequence is often more useful than focusing on panel size:

1. Define the immune phenotype first. Establish which arm of the immune system appears abnormal and whether the findings are persistent, reproducible, and clinically meaningful.

2. Estimate the likelihood of a monogenic disorder. The combination of early onset, severe or opportunistic infection, autoimmunity, cytopenias, syndromic findings, and family history generally carries more diagnostic weight than infection count alone.

3. Select the test based on uncertainty. Use a targeted assay when the phenotype is narrow and a broader approach when several disease mechanisms remain plausible.

4. Review technical coverage before ordering. Confirm whether the assay can detect the variant classes and difficult genomic regions relevant to the suspected condition.

5. Plan for negative and uncertain results. Decide in advance whether the next step will be reanalysis, confirmatory testing, a different sequencing method, or continued clinical monitoring.

6. Link results to management. A pathogenic result may affect vaccination decisions, antimicrobial prophylaxis, immunoglobulin replacement, transplant evaluation, family testing, or surveillance for non-immune complications—but the action depends on the specific disorder.

7. Revisit the diagnosis over time. The immune phenotype can evolve, and variant classifications can change as new evidence becomes available.

This longitudinal approach protects against two opposite errors: dismissing a child because the first panel was negative, and over-treating a child because the first report contained an uncertain variant.

For a child with a high-risk clinical presentation, the priority remains safe management while the diagnostic process continues. If severe combined immunodeficiency is suspected, for example, newborn screening for SCID and urgent cellular immune evaluation may be more time-sensitive than waiting for broad sequencing. Genetic testing can refine the diagnosis and guide family counseling, but it should not delay appropriate clinical action when the immune cascade is already showing signs of serious dysfunction.

The long-term value of getting the strategy right

A molecular diagnosis is most valuable when it changes the child’s care in a meaningful way. It may clarify prognosis, identify complications that require surveillance, guide selection of antimicrobial or immune-directed therapy, support transplant planning, or allow testing of siblings and other relatives. It can also give families a more accurate framework for reproductive counseling and future pregnancies.

But diagnostic success should not be measured only by whether a gene appears on the report. A well-designed pathway also prevents harm: unnecessary procedures, inappropriate treatment, repeated testing, avoidable expense, and prolonged uncertainty created by poorly interpreted VUS findings.

When we choose between a primary immunodeficiency genetic panel and whole exome sequencing, we are not choosing between a “small” and a “large” test. We are choosing how to manage uncertainty. The most appropriate option depends on the clinical presentation, the quality of the immune data, the laboratory’s technical capabilities, the likelihood that the result will alter care, and the financial route available to the family.

For some children, a focused panel remains the fastest and clearest route. For others, WES from the beginning may avoid sequential testing and reduce the total diagnostic burden. In either case, the result must be interpreted alongside the child’s immune phenotype, not in isolation from it.

The long-term prognosis is strongest when diagnosis and management move together: objective immune assessment, carefully selected sequencing, thoughtful interpretation, and continued follow-up as both the child and the science develop. Genetic testing can be a powerful part of that process—but only when the test is chosen with the same clinical precision we apply to the treatment that follows.