Soluble IL 2 Receptor (Sendout)

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

Test Information: The soluble interleukin-2 receptor level is measured by a solid-phase, two-site chemiluminescent immunometric assay. A luminometer reads the light produced, converts it to counts per second, and, using the standard curve recorded in the machine, converts to units per mL (U/mL). Basiliximab binds with the IL-2R in vivo. Results for patients on basiliximab reflect the unbound portion of sIL2R in the plasma sample.

Ordering Requirements: Submit orders via Epic. A completed Cincinnati Children's Hospital requisition is not required.

***Order Alert: Effective 10/03/2025, this test is temporarily unavailable at Cincinnati Children's Laboratory due to a reagent shortage. Testing is expected to resume by mid November 2025. In the interim, samples will be forwarded to ARUP Laboratories for Interleukin 2 Receptor, Soluble, Serum and reported as "ARUP Miscellaneous Frozen Test (Sendout)." The reference range and units will differ from those at Cincinnati Children's Lab due to the different methodology.***

Note: The reference range and units for the ARUP test differ from those at Cincinnati Children's Lab due to a different methodology.

ARUP Laboratories (Temporary Sendout):

Cincinnati Children's Hospital Laboratories:

Outside Laboratories: Centrifuge sample and aliquot serum 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): 1 year; Ambient: 30 minutes; Refrigerated: Unacceptable.

SPS:

• Centrifuge sample and aliquot serum to a separate vial within 2 hours of collection. Freeze serum immediately at -20°C.
• Add on the ARUP Miscellaneous Frozen Test (Sendout) [RARUPZ] (see login information below). Leave the RSIL2R pending for CAST to resolve (do not credit or cancel).

Sendouts:

• Order ARUP Test: 0051529
• Interfaced: Yes [If reordered as RARUPZ. Interface: 602; Department: ARPZ]

Stability: Frozen (required): 1 year; Ambient: 30 minutes; Refrigerated: Unacceptable.