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Test Code LAB113 Phosphorus, Blood

Performing Laboratory

St. Louis Children's Hospital Laboratory - Chemistry

Specimen Requirements

Note: This test is also available as part of LAB20, Hepatic Function Panel. See Common Panel Test Combinations to avoid duplicate requests if needed.

 

Patient Preparation: None

Collection Container/Tube:

Preferred: Mint green-top Lithium Heparin (MNTGRN LiHep) tube

Acceptable: Green samplette/microtainer, plain red-top tube, Gold SST gel tube, or Lavender-top (EDTA) tube

Submission Container/Tube: If specimen is coming from outside facility and collected in a microtainer, plain red-top tube, or lavender-top tube aliquot processed sample into a plastic vial for transport (labeling with specimen type).

Specimen Collection Volume: 1.0 mL (minimum 0.6 mL)

Special Instructions: Send to lab promptly.

 

Sample Rejection

Mislabled or unlabeled specimens

Logistics

Test Availability: Monday-Sunday

Cut-off time: None, performed as received

Turnaround Time: Same Day; 2 hours from receipt in performing lab

Reference Values

Reference Interval: (plasma or serum)

<30 days 4.0-9.0 mg/dL
30 days-1 year: 3.5-7.0 mg/dL
1-12 years: 3.0-6.0 mg/dL
12-15 years: 2.8-5.5 mg/dL
15-18 years: 2.5-5.0 mg/dL
> or= 18 years: 2.3-4.5 mg/dL

Critical Value: 

<30 days: <1.0 mg/dL  OR   >11.0 mg/dL
≥ 30 days: <1.0 mg/dL  OR  >8.0 mg/dL

Critical test results will be automatically called initially and every 24 hours thereafter.

 

Methodology

Molybdate UV

Limitations

  • Phospholipids contained in liposomal drug formulations (eg, AmBisome) may be hydrolyzed in the test due to the acidic reaction pH and thus lead to elevated phophate results.
  • In very rare cases gammopathy, in particular type IgM (Waldenstrom's macroglobulinemia) may cause unreliable results.

Additional Information

FOR SLCH CORE LABORATORY USE ONLY

Lab Processing Instructions: Centrifuge to separate within 4 hours of collection. If specimen is collected in microtainer, plain red-top tube, or lavender-top tube aliquot sample into a Roche false-bottom tube for testing (labeling aliquot with specimen type).

Processed Volume: 0.3 mL plasma/serum

Analyte Stability:

Specimen Type Temperature Time
Whole Blood (unprocessed)  Ambient 4 hours
Plasma/Serum (processed) Refrigerated (preferred)    7 days
  Ambient  24 hours
  Frozen  2 months    

 

 

Test Classification and CPT Code

84100

LOINC

2777-1

Last Reviewed

06/2025