For a woman presenting with depressive symptoms, what is the next best diagnostic step?

For a woman presenting with depressive symptoms, questioning the patient about previous manic episodes is the most appropriate next step to consider. This approach is critical because it helps in assessing whether the patient's depressive symptoms may be part of a bipolar disorder rather than unipolar depression. Exploring the patient's history of mood episodes, particularly manic or hypomanic episodes, is essential for accurate diagnosis and treatment planning.

In cases of suspected bipolar disorder, recognizing the possibility of a manic episode can significantly alter the management approach, as mood stabilizers or atypical antipsychotics may be more appropriate than traditional antidepressants, which could potentially exacerbate manic symptoms.

The other options, while potentially useful in certain contexts, are not as directly relevant for establishing a diagnosis in this scenario. Administering a questionnaire or performing a metabolic panel may help in understanding the patient's overall health status or level of depression, but they do not specifically address the need to assess for bipolar disorder. A urine toxicology screen could be helpful if substance use is suspected but does not directly contribute to the differential diagnosis of depressive versus bipolar disorders.