Staging model, biomarker proposed for bipolar disorder

Mar 27 2014

By Lucy Piper, Senior medwireNews Reporter

Researchers have proposed a model of early and late staging for patients with bipolar disorder according to functioning, number of episodes, age at onset and the time elapsed since first episode.

They also found that interleukin (IL)-6 was a valid biological marker for their proposed staging, with levels increasing in line with neuroprogression of bipolar disorder from first-degree relatives of patients diagnosed with the disorder through to patients categorised as being in the late stage.

“Advocating for a model of staging in [bipolar disorder] that can group the patients according to quantitative cutoffs of common practice clinical variables as well as defining a biochemical correlation is a further step toward establishing a model of staging in [bipolar disorder]”, says the team, led by Eduard Vieta (Hospital Clinic, Barcelona, Spain).

“The implementation of a valid staging classification in [bipolar disorder] may facilitate the identification of rational therapeutic targets and the potential benefit from providing the most effective and less toxic intervention in a time-sensitive manner.”

The researchers gathered sociodemographic, clinical and functional data on a historic cohort of 115 patients with bipolar disorder who were not in an acute episode and 25 of their first-degree relatives.

Functional outcome, as measured on the Functional Assessment Short test, was significantly impaired in patients compared with their first-degree relatives.

And at empirical cutoffs for this test and for the number of episodes, age at onset of the disorder and time elapsed since first episode, cluster analysis divided the patients into two relatively equitable groups of early and late stage.

Early-stage patients tended to have better functioning, fewer episodes and were older at the onset of their disorder, whereas late-stage patients presented with a higher number of episodes, poorer functioning and a greater time since their first episode.

Logistic regression analysis of several possible biomarkers, including serum cytokines, brain-derived neurotrophic factor, and biomarkers of lipid and protein oxidation showed that IL-6 was a viable biomarker.

Patients with bipolar disorder in the early stage had lower levels of IL-6, while those in the late stage had higher levels indicative of an increased inflammatory state.

Indeed, IL-6 levels differentiated patients in the late stage from those in the early stage at an odds ratio of 2.03.

The researchers conclude in Acta Psychiatrica Scandinavica that “the staging model stresses specific intervention and its possibilities to modify the course of the disorder by preventing the progression to a malignant and treatment resistant pattern.”

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