Diagnostic terms to understand

Here we focus on several older terms that you may encounter during the process of diagnosis. We’ll also look at several common misconceptions about MS that you should be aware of from the start.

Older diagnostic terms

Terminology used to describe diagnosis in MS has evolved over time, from Schumacher criteria to Poser criteria to McDonald criteria, while the requirements of dissemination in time and dissemination in space have not changed over time. Earlier diagnostic criteria, such as the Poser Committee Criteria, included categories of definite forms of MS, such as clinically definite MS and laboratory-supported definite MS, and probable forms of MS, such as clinically probable MS and laboratory-supported probable MS. The Poser Committee Criteria relied on dissemination in time and space, but also used new laboratory tests that became available, including cerebrospinal fluid (CSF) analysis and evoked potentials testing. The Poser criteria are shown below.

Poser Committee Criteria for Diagnosis of MS



Clinical lesions

Laboratory or paraclinical lesions

CSF evidence

1. Clinically definite MS 2 2
2 1 and 1
2. Laboratory-supported definite MS 2 1 or 1 +
1 2 +
1 1 and 1 +
3. Clinically probable MS 2 1
1 2
1 1 and 1
4. Laboratory-supported probable MS 2 +


Clinically definite MS. This diagnostic category is, as the term implies, an absolute or definite diagnosis of MS that can be substantiated based on exclusively or almost exclusively clinical evidence.

Laboratory-supported definite MS. This diagnostic category is also an absolute or definite diagnosis of MS made mostly on the basis of clinical evidence, but with supporting evidence provided by laboratory results, including CSF and evoked potentials.

Clinically probable and laboratory-supported probable MS. With both of these categories, there is less confidence in the diagnosis of MS. A person diagnosed with probable MS would receive a definite MS diagnosis once the requirements for both dissemination in time and in space are satisfied.

Written by: Jonathan Simmons | Last reviewed: May 2015.