The Application dimension of Immuno-oncology Diagnosis segmentation delineates how diagnostic tools are deployed across the therapeutic continuum. Predictive biomarker testing, accounting for roughly 40 % of market revenue, enables clinicians to identify patients who are most likely to respond to checkpoint inhibitors, thereby guiding first‑line regimen selection. Companion diagnostic testing, estimated at 30 %, is co‑developed with specific immunotherapies and is mandatory for regulatory approval, creating a tightly coupled demand stream. Prognostic testing, representing about 20 %, assesses disease trajectory independent of treatment choice, informing surveillance strategies and risk stratification. Therapeutic monitoring, the smallest slice at 10 %, tracks dynamic changes in immune markers during treatment, supporting dose adjustments and early detection of resistance. Collectively, these application categories shape the overall market size by allocating investment, R&D focus, and reimbursement pathways, illustrating the nuanced demand drivers within the Immuno-oncology Diagnosis market.