Only 40% of clinicians make a correct diagnosis of bipolar disorder when presented with a definitive case and are subject to heuristic bias, a survey shows.

Clinicians were more likely to make a correct diagnosis when more symptoms were present - meaning patients who just meet the threshold criteria are at risk for undertreatment, report Larissa Wolkenstein (University of Tübingen, Germany) and colleagues.

“Given the high prevalence and the high suicidal risk of bipolar disorder, it seems essential that clinicians are well trained to diagnose bipolar disorder correctly,” they comment in the Journal of Affective Disorders.

Some studies have shown heuristic bias in bipolar disorder diagnosis, for example giving disproportionate weight to certain “prototypic symptoms” such as reduced need for sleep.

To investigate further, the researchers presented a case vignette that fulfilled the criteria for bipolar disorder to 204 psychotherapists.

The basic vignette was a patient who presented with depression and evidence of three out of the seven possible hypomanic symptoms on the DSM-IV. This was modified to include an additional fourth hypomanic symptom of reduced need for sleep or distractibility - thus giving three variant vignettes.

In addition, half of all vignettes included a potential casual explanation for hypomania - meeting a new partner (which does not preclude a diagnosis on the DSM-IV).

Overall, bipolar disorder was correctly diagnosed in 41.0% of the cases; in 59.0% of the cases another diagnosis was made, mainly unipolar depression (50.3%). Seven (3.8%) of those therapists, however, made a note indicating that they suspected a diagnosis of bipolar disorder.

Analysis showed that case vignettes with four hypomanic symptoms were more often diagnosed correctly (for reduced sleep, 47.3% and distractibility, 57%) than were those with only the basic three symptoms (20%), giving a significant odds ratio for misdiagnosis of 5.5, when only the basic three symptoms were present.

Regression analysis revealed no significant difference between the additional symptoms in terms of correct diagnosis, suggesting the clinicians were working on an additive model, which is at odds with the polythetic model of the DSM.

There was a borderline significant trend for a causal influence on diagnosis, such that vignettes where the case reported recently meeting a new partner were slightly less likely to be correctly diagnosed as having bipolar disorder.

Finally, the researchers found that clinicians who misdiagnosed were less likely to recommend appropriate medication.

“Given that therapeutic strategies depend on the assigned diagnostic label, which might not only be inefficient but even harmful when making a wrong diagnostic decision, it becomes clear that a standardized diagnostic proceeding is in great demand,” Wolkenstein et al comment.

MedWire (www.medwire-news.md) is an independent clinical news service provided by Current Medicine Group, a trading division of Springer Healthcare Limited. © Springer Healthcare Ltd; 2010

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Study findings highlight the need for clinicians to recognize comorbid eating disorders in patients with bipolar disorder.

M Fornaro (University of Genoa, Italy) and colleagues found that one in three women with bipolar disorder had at least one eating disorder. Also, the presence of comorbid eating disorders may influence both the clinical characteristics and course of bipolar disorder.

The researchers assessed the prevalence of comorbid DSM-IV-defined anorexia nervosa (AN), bulimia nervosa (BN), and binge eating disorder (BED) in 148 women with a lifetime history of bipolar I disorder, bipolar II disorder, and/or cyclothymia.

In all, 46 (31%) of the patients reported a lifetime history of at least one eating disorder. AN was the most common, affecting 23 (15.5%) patients, followed by BED and BN, which affected 21 (14.2%) and eight (5.4%) patients, respectively. Six (4.1%) patients reported multiple lifetime eating disorders.

As expected, the researchers found that body mass index was highest in patients with BED and lowest in patients with AN.

Fornaro et al also note in the Journal of Affective Disorders that “the presence of BED among bipolar disorder patients has relevant clinical and therapeutic implications.”

They explain: “In these patients the use of anti-dopaminergic drugs may induce weight gain not only by an appetite increase, but also favoring impulsive eating.”

The type of eating disorder did not influence clinical characteristics such as diagnostic distribution, psychotic and melancholic features, suicidal thoughts and attempts, hospitalization, seasonal pattern, post-partum onset, or premenstrual dysphoria.

The researchers suggest that the female-only sample and the small number of women with eating disorders may have affected the ability of the study to detect group differences.

However, women with comorbid BED were more likely than women with comorbid AN and those without eating disorders to experience rapid cyclicity (42.9% versus 32.0% and 18.6%, respectively) and comorbid drug abuse (28.5% versus 16.0% and 20.7%, respectively).

“Our results prompt for the recognition of [eating disorder] comorbidity among bipolar spectrum patients, indicating that BED and AN may influence in different extents both clinical characteristics and course of the illness,” says the team.

“Focusing on a ‘BED versus non-BED’ distinction, potentially relevant therapeutic implications should also be taken into account.”

MedWire (www.medwire-news.md) is an independent clinical news service provided by Current Medicine Group, a trading division of Springer Healthcare Limited. © Springer Healthcare Ltd; 2010

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