Affective dimensions aid bipolar disorder diagnosis

Oct 3 2013

By Lucy Piper, Senior medwireNews Reporter

Measuring affective dimensions can help clinicians diagnose bipolar disorder in patients with first-episode psychosis, researchers report.

Their study findings showed that of the four affective dimensions – depressive, manic, activation, and dysphoric – the activation and manic dimensions discriminated between patients with bipolar disorder and true psychosis and predicted a bipolar diagnosis at 5 years with high levels of sensitivity and specificity.

“The activation dimension alone and combined with the manic dimension offered the best predictive value for diagnosing bipolar disorder,” note lead researcher Ana Maria González-Pinto (Araba University Hospital, Vitoria-Gasteiz, Spain) and co-workers.

Indeed, they calculated that a 5-year delay in diagnosing bipolar disorder could have been prevented for seven (64%) of 11 patients if both the manic and activation dimensions had been assessed at baseline, or for nine (82%) patients if just the activation dimension was assessed.

Affective dimensions, measured using the Young Mania Rating Scale and Hamilton Depression Rating Scale, were assessed in 82 patients with first-episode psychosis at baseline; 19 were diagnosed with bipolar disorder at baseline and the 5-year follow-up, while 11 were diagnosed with bipolar disorder at the 5-year follow-up having had a different diagnosis previously. The remaining 52 patients were classified as having “other psychosis” at the 5-year mark.

The patients diagnosed with bipolar disorder at baseline had significantly higher manic dimension scores than those with a delayed diagnosis (8.63 vs 6.36), and had higher manic (8.63 vs 4.04), activation (10.32 vs 3.51), and dysphoric dimension scores (11.63 vs 7.38) than patients with other psychosis.

The patients with a delayed bipolar disorder diagnosis also differed from those with other psychosis by having higher manic (6.36 vs 4.04) and activation dimension scores (8.18 vs 3.51).

At a cutoff score of 4, the activation dimension predicted a bipolar disorder diagnosis at 5 years with a sensitivity of 86.2% and a specificity of 71.7%. The positive and negative predictive values were 57.8% and 90.5%, respectively.

The manic dimension, whether assessed alone or in combination with the activation dimension, had similarly high levels of sensitivity (around 80–86%) and negative predictive values (around 85–87%). The specificity and positive predictive values were somewhat lower, but still showed good predictive value.

The researchers note in European Psychiatry that absence of the manic dimension increased the likelihood for bipolar disorder being misdiagnosed, as did the presence of the depressive dimension. The latter was present in just 25% of patients diagnosed with bipolar disorder at baseline, compared with 50% of those diagnosed after 5 years, and 33% of those with other psychoses.

This suggests that “[t]he depressive dimension could be a factor that causes diagnostic confusion,” say González-Pinto and team.

They conclude: “Although further research is needed, our findings support the use of a combined categorical and dimensional approach to the diagnosis of mental disorders.”

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