Tex. Civil Practice and Remedies Code § 74.353

(a) On motion of a claimant filed not later than 30 days after the date each defendant's original answer is filed, a court may issue a preliminary determination regarding whether a claim made by the claimant is a health care liability claim for the purposes of Section 74.351.

(b) If a court determines under Subsection (a) or (c) that a claim is a health care liability claim for purposes of Section 74.351, the claimant shall serve an expert report as required by Section 74.351 not later than the later of:

(1) 120 days after the date each defendant's original answer is filed;

(2) 60 days after the date the court issues the preliminary determination under Subsection (a) or (c); or

(3) a date agreed to in writing by the affected parties.

(c) If a court does not issue a preliminary determination under Subsection (a) before the 91st day after the date that a claimant files a motion under that subsection, the court shall issue a preliminary determination that the claim is a health care liability claim for the purposes of Section 74.351.

(d) A preliminary determination under this section is subject to interlocutory appeal by either the claimant or defendant.

(e) If on interlocutory appeal an appellate court reverses a trial court's preliminary determination that a claim is not a health care liability claim, the claimant shall serve an expert report as required by Section 74.351 not later than 120 days after the date that the appellate court issues an opinion reversing the preliminary determination.

(f) A preliminary determination under this section applies only to the issue of whether a claimant is required to serve an expert report under Section 74.351.