Ameriprise details 10.7% Quanterix (QTRX) ownership in Schedule 13G/A

Rhea-AI Filing Summary

Quanterix Corp. received an amended Schedule 13G/A showing that a group of affiliated Ameriprise entities collectively report beneficial ownership of 4,996,073 shares of Quanterix common stock, representing 10.7% of the class as of 12/31/2025.

The filing lists Ameriprise Financial, Inc. and multiple UK- and Luxembourg-based subsidiaries with shared voting and dispositive power over these shares. The Ameriprise entities state the holdings are maintained in the ordinary course of business and not for the purpose of changing or influencing control of Quanterix.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 4)

Quanterix Corp.

(Name of Issuer)

Common Stock

(Title of Class of Securities)

74766Q101

(CUSIP Number)

12/31/2025

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

SCHEDULE 13G

CUSIP No. 74766Q101

1

Names of Reporting Persons

Ameriprise Financial, Inc.

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 4,986,032.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 4,996,073.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

4,996,073.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

10.7 %

12

Type of Reporting Person (See Instructions)

HC

SCHEDULE 13G

CUSIP No. 74766Q101

1

Names of Reporting Persons

TAM UK International Holdings Limited

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

UNITED KINGDOM

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 3,122,967.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 3,122,967.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

3,122,967.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

6.7 %

12

Type of Reporting Person (See Instructions)

FI

SCHEDULE 13G

CUSIP No. 74766Q101

1

Names of Reporting Persons

Threadneedle Holdings Limited

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

UNITED KINGDOM

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 1,228,954.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 1,228,954.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,228,954.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

2.6 %

12

Type of Reporting Person (See Instructions)

FI

SCHEDULE 13G

CUSIP No. 74766Q101

1

Names of Reporting Persons

TAM UK Holdings Limited

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

UNITED KINGDOM

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 1,228,954.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 1,228,954.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,228,954.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

2.6 %

12

Type of Reporting Person (See Instructions)

FI

SCHEDULE 13G

CUSIP No. 74766Q101

1

Names of Reporting Persons

Threadneedle Asset Management Holdings Limited

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

UNITED KINGDOM

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 1,228,954.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 1,228,954.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,228,954.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

2.6 %

12

Type of Reporting Person (See Instructions)

FI

SCHEDULE 13G

CUSIP No. 74766Q101

1

Names of Reporting Persons

TC Financing Ltd

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

UNITED KINGDOM

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 1,228,954.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 1,228,954.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,228,954.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

2.6 %

12

Type of Reporting Person (See Instructions)

FI

SCHEDULE 13G

CUSIP No. 74766Q101

1

Names of Reporting Persons

Threadneedle Asset Management Limited

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

UNITED KINGDOM

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 1,228,954.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 1,228,954.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,228,954.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

2.6 %

12

Type of Reporting Person (See Instructions)

FI

SCHEDULE 13G

CUSIP No. 74766Q101

1

Names of Reporting Persons

Threadneedle Investment Services Limited

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

UNITED KINGDOM

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 1,228,954.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 1,228,954.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,228,954.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

2.6 %

12

Type of Reporting Person (See Instructions)

FI

SCHEDULE 13G

CUSIP No. 74766Q101

1

Names of Reporting Persons

Threadneedle Management Luxembourg S.A.

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

LUXEMBOURG

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 1,894,013.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 1,894,013.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,894,013.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

4.1 %

12

Type of Reporting Person (See Instructions)

FI

SCHEDULE 13G

Item 1.
(a)	Name of issuer: Quanterix Corp.
(b)	Address of issuer's principal executive offices: 900 Middlesex Turnpike, Billerica, MA 01821
Item 2.
(a)	Name of person filing: (a) Ameriprise Financial, Inc. ("AFI") (b) TAM UK International Holdings Limited ("TAMUKI") (c) Threadneedle Holdings Limited ("THL") (d) TAM UK Holdings Limited ("TUHL") (e) Threadneedle Asset Management Holdings Limited ("TAMHL") (f) TC Financing Ltd ("TCFL") (g) Threadneedle Asset Management Limited ("TAML") (h) Threadneedle Investment Services Limited ("TISL") (i) Threadneedle Management Luxembourg S.A. ("TML") Persons (a) through (i) are sometimes referred to herein as the "Ameriprise Entities".
(b)	Address or principal business office or, if none, residence: (a) 145 Ameriprise Financial Center, Minneapolis, MN 55474 (b) Cannon Place, 78 Cannon Street, London, EC4N 6AG (c) Cannon Place, 78 Cannon Street, London, EC4N 6AG (d) Cannon Place, 78 Cannon Street, London, EC4N 6AG (e) Cannon Place, 78 Cannon Street, London, EC4N 6AG (f) Cannon Place, 78 Cannon Street, London, EC4N 6AG (g) Cannon Place, 78 Cannon Street, London, EC4N 6AG (h) Cannon Place, 78 Cannon Street, London, EC4N 6AG (i) 6E, route de Treves, L-2633, Senningerberg, Grand Duchy of Luxembourg
(c)	Citizenship: (a) Delaware (b) United Kingdom (c) United Kingdom (d) United Kingdom (e) United Kingdom (f) United Kingdom (g) United Kingdom (h) United Kingdom (i) Luxembourg
(d)	Title of class of securities: Common Stock
(e)	CUSIP No.: 74766Q101
Item 3.	If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)	Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)	Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)	Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)	Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)	An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)	An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)	A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)	A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)	A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)	A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:
(k)	Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.	Ownership
(a)	Amount beneficially owned: Incorporated by reference to Items (5)-(9) and (11) of the cover page pertaining to each reporting person. AFI, as the parent company of the other Ameriprise Entities, may be deemed to beneficially own the shares reported herein by those reporting persons. Accordingly, the shares reported herein by AFI include those shares separately reported herein by those reporting persons. Each of the Ameriprise Entities disclaims beneficial ownership of any shares reported on this Schedule.
(b)	Percent of class: The information required by Item 4(b) is set forth in Rows (5)-(9) and (11) of the cover page for each Reporting Person hereto and is incorporated herein by reference for each Reporting Person.
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: The information required by Item 4(c) is set forth in Rows (5)-(9) and (11) of the cover page for each Reporting Person hereto and is incorporated herein by reference for each Reporting Person.
	(ii) Shared power to vote or to direct the vote: The information required by Item 4(c) is set forth in Rows (5)-(9) and (11) of the cover page for each Reporting Person hereto and is incorporated herein by reference for each Reporting Person.
	(iii) Sole power to dispose or to direct the disposition of: The information required by Item 4(c) is set forth in Rows (5)-(9) and (11) of the cover page for each Reporting Person hereto and is incorporated herein by reference for each Reporting Person.
	(iv) Shared power to dispose or to direct the disposition of: The information required by Item 4(c) is set forth in Rows (5)-(9) and (11) of the cover page for each Reporting Person hereto and is incorporated herein by reference for each Reporting Person.
Item 5.	Ownership of 5 Percent or Less of a Class.
	Not Applicable
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	Not Applicable
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	If a parent holding company has filed this schedule, pursuant to Rule 13d-1(b)(ii)(G), so indicate under Item 3(g) and attach an exhibit stating the identity and the Item 3 classification of the relevant subsidiary. If a parent holding company has filed this schedule pursuant to Rule 13d-1(c) or Rule 13d-1(d), attach an exhibit stating the identification of the relevant subsidiary. AFI: See Exhibit I
Item 8.	Identification and Classification of Members of the Group.
	Not Applicable
Item 9.	Notice of Dissolution of Group.
	Not Applicable

Item 10.

Certifications:

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Ameriprise Financial, Inc.

Signature:	/s/ Michael G. Clarke
Name/Title:	Michael G. Clarke, Senior Vice President, North America Head of Operations & Investor Services
Date:	02/17/2026

TAM UK International Holdings Limited

Signature:	/s/ Michael G. Clarke
Name/Title:	By: Columbia Mgmt. Investment Advisers, LLC, as Attorney in Fact, By: Michael G. Clarke, SVP, North America Head of Operations & Investor Services
Date:	02/17/2026

Threadneedle Holdings Limited

Signature:	/s/ Michael G. Clarke
Name/Title:	By: Columbia Mgmt. Investment Advisers, LLC, as Attorney in Fact, By: Michael G. Clarke, SVP, North America Head of Operations & Investor Services
Date:	02/17/2026

TAM UK Holdings Limited

Signature:	/s/ Michael G. Clarke
Name/Title:	By: Columbia Mgmt. Investment Advisers, LLC, as Attorney in Fact, By: Michael G. Clarke, SVP, North America Head of Operations & Investor Services
Date:	02/17/2026

Threadneedle Asset Management Holdings Limited

Signature:	/s/ Michael G. Clarke
Name/Title:	By: Columbia Mgmt. Investment Advisers, LLC, as Attorney in Fact, By: Michael G. Clarke, SVP, North America Head of Operations & Investor Services
Date:	02/17/2026

TC Financing Ltd

Signature:	/s/ Michael G. Clarke
Name/Title:	By: Columbia Mgmt. Investment Advisers, LLC, as Attorney in Fact, By: Michael G. Clarke, SVP, North America Head of Operations & Investor Services
Date:	02/17/2026

Threadneedle Asset Management Limited

Signature:	/s/ Michael G. Clarke
Name/Title:	By: Columbia Mgmt. Investment Advisers, LLC, as Attorney in Fact, By: Michael G. Clarke, SVP, North America Head of Operations & Investor Services
Date:	02/17/2026

Threadneedle Investment Services Limited

Signature:	/s/ Michael G. Clarke
Name/Title:	By: Columbia Mgmt. Investment Advisers, LLC, as Attorney in Fact, By: Michael G. Clarke, SVP, North America Head of Operations & Investor Services
Date:	02/17/2026

Threadneedle Management Luxembourg S.A.

Signature:	/s/ Michael G. Clarke
Name/Title:	By: Columbia Mgmt. Investment Advisers, LLC, as Attorney in Fact, By: Michael G. Clarke, SVP, North America Head of Operations & Investor Services
Date:	02/17/2026

Comments accompanying signature: Contact Information Charles Chiesa VP Fund Treasurer Global Operations and Investor Services Telephone: 617-385-9593

Exhibit Information

Exhibit Index Exhibit I Identification and Classification of the Subsidiaries which Acquired the Security Being Reported on by the Parent Holding Company. Exhibit II Joint Filing Agreement Exhibit III Powers of Attorney

FAQ

What does the Ameriprise Schedule 13G/A reveal about Quanterix (QTRX)?

The filing shows Ameriprise entities beneficially own 4,996,073 Quanterix common shares, or 10.7% of the class, as of 12/31/2025. The stake is reported as held in the ordinary course of business, without the stated intent to influence or change control of Quanterix.

Which Ameriprise entities report ownership in Quanterix (QTRX)?

Ameriprise Financial, Inc. and several affiliates, including UK International Holdings Limited and Threadneedle-branded UK and Luxembourg entities, report Quanterix holdings. Together, these "Ameriprise Entities" disclose shared voting and dispositive power over the reported shares, with Ameriprise Financial deemed to beneficially own shares held by its subsidiaries.

How large is Ameriprise’s reported stake in Quanterix (QTRX)?

Ameriprise entities report beneficial ownership of 4,996,073 Quanterix common shares, representing 10.7% of the outstanding class as of 12/31/2025. Individual subsidiaries show portions of this stake, such as 3,122,967 shares or 6.7% and 1,894,013 shares or 4.1%, under shared voting and dispositive power.

Is Ameriprise seeking control of Quanterix (QTRX) with this ownership?

The Ameriprise entities certify the Quanterix shares were acquired and are held in the ordinary course of business, not to change or influence control of the issuer. They also state the holdings are not connected with any transaction intended to affect control, other than limited proxy nomination activities referenced in regulations.

What type of SEC filing is this for Quanterix (QTRX)?

This is an Amendment No. 4 to a Schedule 13G, a passive ownership report. It updates beneficial ownership information for Quanterix common stock by Ameriprise and related entities as of 12/31/2025, detailing share counts, voting power, and percentage of the class for each reporting person.

Who signed the Ameriprise ownership filing for Quanterix (QTRX)?

The statement is signed by Michael G. Clarke, Senior Vice President and North America Head of Operations & Investor Services. Several signatures are executed on behalf of Ameriprise-related entities via Columbia Mgmt. Investment Advisers, LLC acting under powers of attorney referenced in the exhibit index.