Veterans researching medical evidence run into three terms that sound alike: nexus letter, DBQ, and IMO. They serve different purposes, and knowing which is which helps you build the right evidence. This guide breaks them down.
Nexus letter: the connection
A nexus letter is a medical opinion focused on one thing: whether your condition is connected to your service. It states the opinion in VA terms ("at least as likely as not") and explains the medical rationale for the link.
Use it when the service connection is the question, which is the situation for many claims.
DBQ: the severity
A DBQ, or Disability Benefits Questionnaire, is a standardized VA form that documents the current severity of a condition. It captures the specific measurements and findings the VA uses to assign a rating percentage, such as range of motion for a joint or symptom frequency for a mental health condition.
Use it when the diagnosis and connection are settled, but you need to document how severe the condition is for an accurate rating.
IMO: the in-depth opinion
An IMO, or Independent Medical Opinion, is a broader, in-depth medical opinion from a provider independent of the VA. It can address service connection, severity, and complex medical questions in detail. An IMO often goes deeper than a standard nexus letter, which makes it useful for complex or contested claims.
Think of it as the most thorough option when a claim is complicated or has been denied.
They often work together
These are not either-or. A strong claim might use a nexus letter to establish the connection and a DBQ to document severity. A complex appeal might use an IMO to address multiple issues at once.
The right combination depends on your claim: what is being disputed, whether it is a new claim or an appeal, and how complex the medical picture is.
A real-world example
A veteran's claim had two problems: the VA questioned the service connection and had underrated the severity. A nexus letter addressed the connection, and a DBQ documented the severity for a proper rating. Together they covered both gaps.