Private company
Who owns Diagnostic Lab of Michigan, LLC
One company in the researched set discloses a stake in Diagnostic Lab of Michigan, LLC, none of it sized by anyone who discloses it. Diagnostic Lab of Michigan, LLC is private, so no 13F reports it: a 13F covers exchange listed positions only. These figures exist because each holder disclosed the stake in its own filings.
Diagnostic Lab of Michigan, LLC - Profile
- Type
- joint venture
- Based in
- United States
- Founded
- 2026
Diagnostic Lab of Michigan is a clinical laboratory joint venture formed by Quest Diagnostics and Corewell Health, the Michigan health system that runs 21 hospitals, more than 300 outpatient sites and post acute facilities with over 65,000 employees. The transaction closed on 5 January 2026. Quest brings its Collaborative Lab Solutions hospital laboratory management programme, which now covers laboratory operations at all 21 Corewell hospitals and spans supply chain, patient blood and anemia management, laboratory analytics and stewardship and reference testing, while Corewell contributes its existing laboratory network and clinical demand. The venture is building a 100,000 square foot laboratory at the Corewell Health Southfield Center in Southfield, Michigan, equipped with automated microbiology and high throughput molecular testing and expected to open in the first quarter of 2027. Until then the two partners' existing laboratories continue to serve it.
Source
Diagnostic Lab of Michigan, LLC files nothing with the SEC, so none of this comes from a filer record. The description was written for this site in August 2026 from Corewell Health and Quest Diagnostics Complete Laboratory Joint Venture Transaction in Michigan (Quest Diagnostics newsroom, 5 January 2026), Diagnostic Lab of Michigan (Quest Diagnostics facilities page) and Diagnostic Lab of Michigan to Open at Corewell Health Southfield (DBusiness). The ownership figures below come from the holders' filings instead, and are sourced row by row.
The disclosed stakes
One row per position. Where a holder reports the same company in two share classes, both rows are shown rather than summed, because the class is part of a position's identity.
Where each figure comes from
A private stake has no ownership form behind it, so the source is always the holder's own filing or disclosure. Anything modelled says so, with the arithmetic.
- Quest Diagnostics Incorporated. Exhibit 21.1 lists 'Diagnostic Lab of Michigan, LLC (DE)' at 47.19% directly, plus 3.67% held via Quest Diagnostics Clinical Laboratories, Inc. and 0.14% held via AmeriPath Indianapolis, P.C. (both wholly Quest-owned entities), for a stated Quest group total of 47.19 + 3.67 + 0.14 = 51.00%, written here as 51.0, not 0.51. This is a pre-existing Michigan joint venture, distinct from the new Corewell Health venture (also in Michigan but a separate legal entity formed in Jan 2026; Corewell does not appear anywhere in Exhibit 21.1, likely because it closed after the exhibit's cutoff or falls under a different immateriality threshold). No individual carrying value is disclosed for this entity in the 10-K or 10-Q. source
What this page is not
It is not a complete register. It lists the holders who happen to be inside the researched set and disclosed the stake themselves. A private company can have many other shareholders, and nothing here rules them out: venture investors, founders and employees usually appear in no public filing at all. Percentages are of Diagnostic Lab of Michigan, LLC where a holder stated one, and are missing where no holder did.