DGX vs OPK: Which Is the Better Buy in 2026?

Same yardstick, side by side (as of August 2026). Valuation lined up like this is most meaningful for two names in the same corner of the market, which these are. Figures are approximate; verify before investing.

The metrics above tell you which is the marginally better business. The bigger risk for most people is not picking the slightly worse stock, it is over-concentrating. DGX and OPK share themes, so owning both, or adding either to what you already hold, can quietly push a large share of your portfolio into one bet.

This is the part a generic comparison page cannot answer, because it depends on what you own. Connect your brokerage and Walnut shows your real, combined DGX and OPK exposure, flags overlap with your existing positions, and tells you if adding one would tip you past a concentration you are comfortable with, read-only by default, with your login staying at your broker. Walnut is not an investment adviser.

Quest Diagnostics operates one of the largest clinical laboratory networks in the United States, processing billions of test results a year across a footprint of patient service centers, hospital and physician outreach relationships, and consumer-initiated testing. Its core Diagnostic Information Services segment spans routine testing (blood counts, cholesterol, metabolic panels) plus a growing base of advanced molecular and genomic diagnostics in oncology, neurology, women's health, and infectious disease. Scale, a national logistics network, and long-standing payer contracts are the company's main moats in a fragmented roughly $100 billion US lab market where Quest and Labcorp together hold the top tier.

Full DGX guide

OPKO Health, Inc. is a diversified healthcare company that operates across three areas. Its diagnostics business is anchored by BioReference Laboratories, a clinical lab whose revenue has been shrinking after the company sold certain assets (including oncology testing assets to Labcorp) and narrowed its geographic footprint to cut losses; its 4Kscore prostate-cancer test is a growth focus. Its pharmaceutical segment sells products such as Rayaldee (for secondary hyperparathyroidism) and earns a profit share on NGENLA, a long-acting growth-hormone product commercialized globally by Pfizer. Its third and most speculative piece is ModeX Therapeutics, a clinical-stage biotech developing multispecific antibodies and vaccines, including MDX2001, a tetraspecific T-cell engager for solid tumors that has advanced through early-stage dosing.

Full OPK guide

Both fit overlapping themes, but they are not interchangeable. The useful comparison is which set of drivers and risks you want exposure to.

• DGX drivers: Organic volume growth; Acquisitions as a growth engine.
• OPK drivers: ModeX pipeline and partnerships; Pharmaceutical royalties and products.

A faster-growing, richer-valued name usually swings harder, so it suits a longer horizon and a higher tolerance for volatility; a steadier, more cash-generative business suits a more conservative or income-minded investor. The honest test is which set of risks you could hold through a drawdown: The largest risk is reimbursement policy: Medicare rates under PAMA face potential cuts (a delay pushed reductions toward 2027, but a roughly 15 percent cut to hundreds of tests looms without permanent reform), and private-payer pricing pressure caps growth. For OPK, the dominant risk is that OPKO has been unprofitable at the consolidated level, with declining revenue as BioReference shrinks, so the base business is not yet self-sustaining.

Growth-minded investors who believe the theme has years to run tend to accept the richer multiple for more upside; value-minded investors lean toward the cheaper forward earnings and steadier profile. Pick DGX if you believe its drivers more; OPK if you believe its. Many investors hold both, but since they share themes, that is a concentrated bet, not diversification. Decide deliberately and check overlap. For the full detail, see the DGX and OPK guides.

DGX. In Q1 2026 Quest reported revenue of about $2.9 billion (up 9.2 percent) and adjusted EPS of $2.50 (up 13.1 percent), and raised full-year guidance. The stock traded near $205 in mid-July 2026 at a forward P/E under 20, a moderate multiple below primary competitor Labcorp. The dividend has risen for 15 consecutive years, most recently a 7.5 percent increase.

OPK. All figures here are approximate and tied to the asOf date; verify live numbers on a current quote page or the latest SEC filing before acting. Because OPKO is unprofitable, standard earnings multiples are not meaningful, and much of the stock's value rests on speculative, milestone-contingent pipeline outcomes at ModeX. Treat any partnership-value figures (such as the over-$1-billion Regeneron framing) as potential future milestones that require clinical and commercial success, not current revenue.

Headline figures (approximate, July 2026): DGX shows revenue (ttm) ~$11.5B, 2026 revenue guidance ~$11.78B to $11.9B, 2026 adj. eps guidance ~$10.63 to $10.83, market cap ~$22.8B; OPK shows revenue trend Declining, largely due to BioReference asset sales and lower test volumes; management guided 2026 total revenue to a range (roughly the low-to-mid-$500 millions). Figures are approximate, verify live., profitability Unprofitable at the consolidated level, posting net losses, though the operating loss has been narrowing on cost cuts and a more focused lab footprint., balance sheet Holds a meaningful cash position alongside debt (roughly balanced net cash/net debt in recent reporting). Confirm current cash and debt on the latest filing., market cap tier Small-cap. Approximate market value has been under roughly $1 billion. Verify the live number..

DGX and OPK are related but distinct: same themes, different businesses and risks. Neither wins in the abstract; the right pick is whichever thesis you actually believe, sized so you are not over-concentrated in one theme. Walnut can show your combined DGX and OPK exposure against your real portfolio. It is not an investment adviser.