CPT 0524U: sFlt‑1/PlGF Ratio Assay for Preeclampsia Diagnosis

CPT code 0524U designates a Proprietary Laboratory Analyses (PLA) test for the PreClaraTMRatio, quantifying the ratio of soluble fms–like tyrosine kinase-1 (sFlt–1) to placental growth factor (PlGF) via immunoassay. This CPT PLA code is specific to Thermo Fisher Scientific's PreClaraTMRatio assay and is used to aid in the diagnosis of preeclampsia by assessing biomarkers associated with placental vascular function. Nationally, the code matters because targeted biomarker assays for preeclampsia are increasingly used to stratify risk, inform clinical decision-making, and influence use of maternal-fetal monitoring resources.

Key payers addressed include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise overview of the clinical purpose of the test, payer coverage context, common billing modifiers, and operational considerations for specimen type and typical site of service. The publication also summarizes expected content areas such as benchmark billing practices, relevant policy or coverage trends for proprietary lab tests, and clinical context for interpretation of an sFlt‑1/PlGF ratio. Data not available in the input will be identified where applicable.

Billing Code Overview

CPT code 0524U is a Proprietary Laboratory Analyses (PLA) code assigned specifically to the PreClaraTMRatio (sFlt–1/PlGF) test from Thermo Fisher Scientific. The assay measures the ratio of soluble fms–like tyrosine kinase-1 (sFlt-1) to placental growth factor (PlGF) using an immunoassay on a serum or plasma sample to aid in the diagnosis of preeclampsia.

Service type: Proprietary laboratory diagnostic immunoassay

Typical site of service: Clinical laboratory or hospital laboratory

Data not available in the input.

Clinical Context

A pregnant patient in the second or third trimester presents to an obstetric clinic or hospital with new-onset hypertension, proteinuria, or symptoms concerning for preeclampsia such as severe headache, visual changes, epigastric pain, or rapid edema. The ordering clinician (maternal-fetal medicine specialist, obstetrician-gynecologist, or labor and delivery physician) requests the PreClaraTMRatio (sFlt–1/PlGF) immunoassay to aid in the diagnostic evaluation and short-term risk stratification for preeclampsia.

The clinical workflow: the patient undergoes venipuncture for serum or plasma collection in an outpatient clinic, antepartum testing unit, emergency department, or inpatient labor and delivery unit. The specimen is labeled and sent to the performing laboratory (or the manufacturer's designated lab) for analysis using the proprietary Thermo Fisher Scientific assay. Results are reported to the ordering clinician and incorporated into clinical decision-making regarding monitoring intensity, timing of delivery, need for transfer to a higher level of maternal-fetal care, or outpatient follow-up. Billing for this proprietary laboratory analysis is reported using 0524U for the specific PreClaraTMRatio test.

Coding Specifications

Modifier	Description	When to Use
`00`	No modifier — standard reporting	Use when no additional modifier applies to the professional or technical components.

Taxonomy Code	Specialty	Notes
207Q00000X	Maternal and Fetal Medicine (Perinatology)	Specialists who manage high-risk pregnancies and commonly order preeclampsia risk testing.
207L00000X	Obstetrics & Gynecology	Obstetricians who evaluate and manage prenatal patients and order diagnostic testing.
208D00000X	Emergency Medicine	Emergency physicians may order the assay when pregnant patients present with acute symptoms suggestive of preeclampsia.
3336C0005X	Clinical Laboratory	Laboratory specialists who perform and validate the proprietary immunoassay.

Related Diagnoses

ICD-10 Code	Description	Clinical Relevance
`O14.03`	Mild pre-eclampsia, third trimester	Direct indication for sFlt-1/PlGF testing to aid diagnosis and risk stratification.
`O14.13`	Severe pre-eclampsia, third trimester	Used when assessing severity and short-term risk of progression; assay results inform monitoring/delivery decisions.
`O14.92`	Pre-eclampsia, unspecified, postpartum	Applied if preeclampsia is suspected or persistent after delivery; assay may be used in select postpartum evaluations.
`O13.9`	Gestational (pregnancy-induced) hypertension without significant proteinuria, unspecified trimester	sFlt-1/PlGF can help distinguish true preeclampsia from gestational hypertension.
`O99.89`	Other specified diseases and conditions complicating pregnancy, childbirth and the puerperium	May be used for related hypertensive or vascular disorders in pregnancy where biomarker testing assists diagnosis.

Related CPT Codes

CPT Code	Description	Relationship to This Procedure
`80048`	Basic metabolic panel	Used to evaluate renal function and electrolytes in patients with suspected preeclampsia; commonly ordered alongside sFlt-1/PlGF testing.
`82043`	Assay of estriol, unconjugated	Data not directly related; included as an example of pregnancy-related serum assays — not routinely paired with sFlt-1/PlGF.
`81025`	Urine pregnancy test, qualitative	Performed earlier in pregnancy; not typically concurrent but part of obstetric workflow.
`99000`	Handling and/or conveyance of specimen	May be used by some facilities for specimen handling fees when applicable to specialized reference testing.
`99070`	Supplies and materials (e.g., sterile trays)	Used when additional supplies are used in the collection or processing of specimens for specialized assays.

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Summary & Overview