Soluble IL 2 Receptor (Sendout)

This test replaces Soluble IL 2 Receptor [RSIL2R]
single page view

General Information

Lab Name
Soluble IL 2 Receptor (Sendout)
Lab Code
RSI2RL
Epic Name
Soluble IL-2 Receptor (Sendout)

Also included in the Hyperinflammatory Lab Panel.
External Test Id
LAB3459, CWA0201
Description

Test Utility: This test is ordered as part of the workup for hyperinflammatory syndromes such as hemophagocytic lymphohistiocytosis (HLH). This test should be ordered concurrently or after Hyperinflammatory Screening Labs have been obtained (CBC with diff, ferritin, fibrinogen, triglycerides, LDH, and D-dimer).

    The following are consistent with, but not specific for, a diagnosis of HLH:

    • Elevated sIL-2R, CXCL-9, and IL-18
    • Elevated sCD163
    • Reduced NK function (or cell surface expression of CD107alpha)
    • Reduced perforin, SAP, or XIAP

    Urgent Testing: Testing is performed at Seattle Children's Hospital Laboratory twice weekly, Tuesday and Friday, with a turnaround time of 4 days from sample receipt. Expedited testing is available Mon-Fri; please contact the Lab Med Resident On-Call to arrange. Morning collections are recommended for STAT orders, as samples must be received in lab at Seattle Children’s before noon for same-day testing.

    Synonyms
    CD25 Soluble, CWA0201, Hemophagocytic lymphohisticytosis, HLH, Hyperinflammatory Disorder, IL-2R, LAB3459, SIL2R, Soluble CD 25, Soluble CD25, Soluble IL-2R, Soluble IL2 Receptor, Soluble Interleukin 2 Receptor
    Components
    Code Name
    RSI2RR Soluble IL 2 Receptor Level

    Interpretation

    Method

    Siemens Immulite

    Reference Range
    See individual components
    Ref. Range Notes

    Reference Ranges:

    <3 years: 398-1940 U/mL
    3-8 years: 144-1329 U/mL
    ≥8 years: 137-838 U/mL

    Note: The reference ranges and units for this test to Seattle Children's Hospital Laboratory match those of the test previously performed by Cincinnati Children's Hospital Laboratory from 10/10/2019 to 10/02/2025. From 10/03/2025 to 02/01/2026, samples referred to ARUP Laboratories were tested using a different methodology and reported with a reference interval of 175.3 pg/mL - 858.2 pg/mL.

    Interferences and Limitations

    Heterophilic antibodies in human serum can react with the immunoglobulins included in the assay components causing interference with in vitro immunoassays. Samples from patients routinely exposed to animals or animal serum products can demonstrate this type of interference potentially causing an anomalous result. These reagents have been formulated to minimize the risk of interference; however, potential interactions between rare sera and test components can occur.

    The drug asfotase alfa (STRENSIQ), a recombinant form of alkaline phosphatase, is expected to interfere with this assay as this assay utilizes an alkaline phospatase detection system.

    Ordering & Collection

    Specimen Type
    Blood
    Collection

    Collect 3 mL blood in LAVENDER TOP (EDTA) tube

    Handling Instructions

    Outside Laboratories: Centrifuge sample and aliquot plasma to a separate vial within 2 hours of collection. Freeze plasma immediately at -20°C while awaiting shipment. Transport on dry ice.

    Stability: Frozen (required): 6 months; Ambient: 30 minutes; Refrigerated: 2 days.

    Quantity
    Requested: 1 mL EDTA plasma
    Minimum: 0.4 mL EDTA plasma

    Processing

    Receiving Instructions

    Centrifuge sample and aliquot plasma to a separate vial within 2 hours of collection. Freeze plasma immediately at -20°C.

    Sendouts:

    • Order SEACHL Test: LAB3459
    • Interfaced: Yes [Interface: 601; Department: SOSC]
    • Send samples on dry ice via DLMP or DE courier with a copy of the MayoAccess Batch Sheet.
    • Urgent Sample Handling: In select cases, providers may arrange with Seattle Children's to perform testing outside of their regular performance days. If approved, the LMR will contact SPS/Sendouts asking lab staff to prioritize transport.
      • Write "STAT" on the outgoing MayoAccess Batch Sheet to ensure urgent processing at intake.
      • Urgent samples should be sent immediately via Delivery Express to ensure that they reach Seattle Children's before the noon cutoff for same-day testing.

    Stability: Frozen (required): 6 months; Ambient: 30 minutes; Refrigerated: 2 days.

    Misc Sendout

    Performance

    Lab Department
    SCHL Interfaced Sendouts(SOSC)
    Frequency
    Performed: Tuesday, Friday. Turnaround Time (Routine): 4 days from sample receipt at Seattle Children's Hospital Lab.
    Available STAT?
    Yes, contact the Laboratory Medicine Resident on-call to arrange for expedited testing.
    Performing Location(s)
    Sendout Seattle Children's Hospital Laboratories
    206-987-2617

    4800 Sand Point Way NE
    Seattle, WA 98105

    Room Number: FB.2.441

    Billing & Coding

    CPT Codes
    83520
    LOINC
    9654-5
    Interfaced Order Code
    UOW6344