Biomarker-guided psychiatric care has expanded substantially in the past decade. The clinical task is to engage the panels with clinical actionability while remaining honest about the limits of newer markers. Established and emerging biomarkers each have specific roles; the discipline is to order what changes treatment decisions and to acknowledge the developing nature of the broader field.
Established biomarkers with routine clinical use. hs-CRP for inflammation-elevated depression (Stage 10.5 and 16) — guides anti-inflammatory augmentation decisions. Comprehensive thyroid panel beyond TSH (Stage 19.5) — identifies subclinical hypothyroidism and low T3 syndrome relevant to TRD. Vitamin D, B12, folate — addresses nutritional contributions. Fasting glucose and A1c — metabolic context including pre-diabetes recognition. Basic metabolic panel for medication monitoring and broader medical context. These are routine workup, not specialty testing.
APOE testing for Alzheimer's risk. APOE4 allele substantially increases AD risk; one copy roughly doubles risk, two copies substantially increases. Testing is now widely available including direct-to-consumer (23andMe variant data). The clinical actionability is mixed — APOE4 positive status modestly changes risk discussion but does not radically change the prevention prescription, which is the Modifiable Twelve factors regardless of APOE status. Some patients are motivated by the information; others find it distressing without clear actionable implication. The conversation requires careful informed consent.
Blood-based AD biomarkers. Plasma amyloid (p-tau217, p-tau181, Aβ42/40 ratio) and neurofilament light chain (NfL) panels are emerging into clinical use, with some now available through commercial labs and some specialty programs. The accuracy compared to CSF and PET is improving substantially. Clinical use is currently in patients with cognitive concerns warranting evaluation; the use as screening in cognitively-healthy adults is more controversial. The field is developing rapidly; what is established in 2026 will likely change substantially over the next several years.
Other emerging panels. Inflammation panels beyond CRP (IL-6, TNF-alpha — research use). Stress and HPA axis panels (selective use; see Stage 19.7). Microbiome panels (research use; clinical actionability limited — Stage 17.1). Comprehensive metabolic biomarkers (lipid subtypes, insulin resistance markers) for cardiovascular and cognitive trajectory. Each has selective clinical use; the broader testing-everything approach produces data without commensurate clinical action. The discipline is to order biomarkers that change treatment decisions, integrate findings with clinical care, and frame the developing nature of the field honestly with patients.