Introduction: The aging of society has increased the incidence of dementia, which is more common among older individuals. Older individuals are typically cared for by primary care providers in hospitals. However, more than 60% of patients with early-stage dementia are unrecognized in primary care. Several groups have developed dementia screening tools for primary care purposes. In this work, assessments based on plasma biomarkers for differentiating among various types of dementia were developed for primary care applications. Methods: Forty-six patients with very mild dementia (VMD) or mild cognitive impairment (MCI), fifty patients with Alzheimer’s disease (AD), and four patients with non-AD dementia were enrolled. Plasma amyloid-beta 1–40 (Aβ1–40), Aβ1–42, total Tau (T-Tau), and phosphorylated Tau (p-Tau181) were assayed using immunomagnetic reduction for each subject. Results: The results show that non-AD dementia can be discriminated from other forms of dementia using plasma Aβ1–40, with a cutoff value of 50.03 pg/ml resulting in an area under the curve (AUC) of 0.794. The plasma Aβ1–42-to-Aβ1–40 ratio can serve as an index for discriminating AD from VMD and MCI, with a cutoff value of 0.3015 resulting in an AUC of 0.674. Discussions: A biomarker panel measuring the levels of plasma Aβ1–40 and the ratio of Aβ1–42 to Aβ1–40 could potentially assist primary care practitioners in evaluating whether a patient suffers from non-AD dementia, AD, or VMD and MCI.