Distinguishing delusional disorder from bipolar in my patient

I'm having a bit of a hard time figuring out what my patient's diagnosis is, are there any pro-tips on how to nail diagnosis of delusional disorder? My patient holds grandiose/persecutory delusions, he does not quite meet criteria for bipolar 1 (+ for insomnia, grandiosity and increase in goal-directed activity) though it is possible that a 4th criteria may have been met previous to his admission. My issue is that I'm not really seeing any major mood symptoms, he is calm and collected... Distinguishing delusional disorder from bipolar in my patient
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