A nexus letter is persuasive when its facts are accurate, its reasoning is spelled out, and it deals with the evidence that points the other way. The Court of Appeals for Veterans Claims put it plainly in Nieves-Rodriguez v. Peake: "It is the factually accurate, fully articulated, sound reasoning for the conclusion, not the mere fact that the claims file was reviewed, that contributes probative value to a medical opinion."

That standard gives you a way to review your own letter before you rely on it. This page shows how opinion quality lined up with Board of Veterans' Appeals outcomes, then walks through a record-by-record check.

What the Board treats as persuasive

The Court decided Nieves-Rodriguez v. Peake, 22 Vet.App. 295, 304 (2008), and the Board cites it routinely, sometimes in a paraphrase. One October 26, 2023 decision (Citation A23029909) put it this way: an opinion that is "factually accurate, fully articulated, and based on sound reasoning carries significant weight." On the same page, the Court said most of an opinion's probative value "comes from its reasoning," and that neither a VA examination nor a private opinion is entitled to any weight "if it contains only data and conclusions." You can read the full opinion on the Court's site.

In practice, the Board discounts opinions for a short list of reasons:

  • A conclusion without reasoning. "At least as likely as not" followed by nothing that explains why.
  • A wrong or incomplete history. The opinion says there was no in-service complaint when a service treatment record shows one, or it never mentions a later injury.
  • A file review offered in place of analysis. Saying the claims file was reviewed does not add weight by itself.
  • The wrong question. In a secondary claim, an opinion that answers only causation leaves aggravation open. The Court of Appeals for Veterans Claims held in El-Amin v. Shinseki, 26 Vet.App. 136 (2013), that such an opinion was not adequate to decide aggravation. The secondary nexus letter guide covers what to ask for.

How opinion quality lined up with Board outcomes

Claim Raven's analysis of Board decisions codes how the Board described the medical opinion on each issue. Counted in condition records (one condition in one decision), the favorable share by opinion quality was:

How the Board described the opinionCondition recordsFavorable
Strong12,50289.7%
Adequate18,59269.2%
Weak18,2533.7%
Missing10,7001.6%

Favorable means granted, partly granted or mixed, out of issues the Board decided (grants, denials and remands). A remand is not counted as favorable.

Read the table with three limits in mind. These are Board appeal outcomes from 2024 to 2025 decisions, a group of already-disputed claims, so they describe patterns, not your odds. The Board's description of an opinion partly reflects its own conclusion, so "strong" and "favorable" are not independent measurements. And a purchased letter does not land in the strong tier because it was purchased. The useful finding is the drop between adequate and weak: a weak opinion did about as well as no opinion. The full tables are on Claim Raven's VA disability statistics page.

Check the letter against the records it cites

Make a two-column list. In the first column, copy every record the letter says the clinician reviewed. In the second, confirm the record exists, the date is right, and the letter describes it accurately.

Watch for statements such as:

  • "There was no complaint in service" when a service record documents one.
  • "Symptoms continued without interruption" when the record shows a long, unexplained gap.
  • "No later injury occurred" when a civilian record shows one.
  • "The condition began after the medication" when the dates show the opposite.

A favorable conclusion built on a wrong fact can be discounted. Do not remove the inconvenient record. Give it to the clinician and ask whether the corrected history changes the opinion. The guide to which records a clinician should review helps you check what the letter was built on.

Test the reasoning

Cover the conclusion and read only the explanation. Then answer:

  1. Which medical facts did the clinician treat as important?
  2. How do those facts support the proposed connection?
  3. What competing cause or contrary evidence did the clinician consider?
  4. Why did the clinician prefer one explanation over another?
  5. What remains uncertain?

A worked example (fictional): A letter says, "The veteran's tinnitus caused insomnia because research shows tinnitus is associated with sleep problems." It names a condition pair and a research finding. It does not give the insomnia diagnosis or its date, the order in which symptoms began, other possible causes, the study itself, or how the study applies to this person. That does not make the conclusion wrong. It means the reasoning shown cannot yet carry it.

Credentials matter in context. The letter should say who the clinician is and why the question fits their training, but a strong signature block does not repair a missing explanation. Probability wording tells the reader how certain the clinician is; it does not substitute for the reasoning that should precede it.

A practical red-flag table

Red flagWhy it mattersFollow-up to request
The records-reviewed list is vagueYou cannot tell whether key facts were consideredA dated list or appendix of records reviewed
A conclusion with no explanationThe Board has nothing to weighThe medical reasoning connecting the facts to the conclusion
An important later injury is missingThe factual basis may be incompleteProvide the record and ask whether it changes the opinion
A study is cited but not appliedA population finding is not an individual opinionHow the study fits this history, and its limits
Causation and aggravation are blended or one is missingThe letter may not answer the claim's questionSeparate answers on causation and on aggravation
No signature, date or credentialsAuthorship and qualification cannot be confirmedA signed, dated final copy with credentials

Ask for clarification, not a rewrite

Give the clinician a short list: the record corrections and the unanswered questions from the table. Do not rewrite their medical reasoning. Keep the original and any revised version so the change is visible.

You can run a letter through Raven Nexus for a free starter check of the letter on its own; comparing it with more records needs Standard or Plus. The tool points out passages that may need clarification. It does not produce a signed medical opinion, and Claim Raven has a commercial interest because it sells the tool. For more examples of what a complete opinion covers for each theory, see the annotated nexus letter examples.

Sources and scope

Checked September 23, 2026: Nieves-Rodriguez v. Peake, 22 Vet.App. 295, 304 (2008) (opinion PDF); El-Amin v. Shinseki, 26 Vet.App. 136, 140 (2013) (opinion PDF), both Court of Appeals for Veterans Claims decisions; 38 C.F.R. § 3.310. Board figures are the audited values from Claim Raven's analysis of the analyzed subset of Claim Raven's 1,871,000+ Board-decision library covering 101,518 condition records. The quality coding comes from how each decision described the opinion, which is why it is reported as an association. This checklist tests whether a letter is complete and internally supported; it cannot tell you whether the medical conclusion is correct.