AGE          MALES/FEMALES
      0 - 3 days     8.0-20.0 μg/dL
      3 - 30 days    5.0-15.0 μg/dL
31 days - 1 years    6.0-14.0 μg/dL
      1 - 5 years    4.5-11.0 μg/dL
      6 - 18 years   4.5-10.0 μg/dL
  Normal adults      4.6 12.0 μg/dL

The assay is unaffected by icterus (bilirubin is less than 37 
mg/dL), hemolysis (Hb is less than 2300 mg/dL), lipemia (triglycerides 
is less than 2500 mg/dL) and biotin is less than 1200 ng/mL (criterion: 
recovery within plus or minus 10% of initial value).

No interference was observed from rheumatoid factor (up to 2400 U/mL) 
and samples from dialysis patients.

In vitro tests were performed on 15 commonly used pharmaceuticals. No 
interference with the assay was found.

Autoantibodies to thyroid hormones can interfere with the assay.  The 
risk of interference from potential immunological interactions between 
test components and rare plasma has been minimized by the inclusion of 
additives.

In rare cases, interference due to extremely high titers of antibodies 
to ruthenium can occur.  T4 reagent contains additives which minimize 
these effects.

Extremely high titers of antibodies to streptavidin can occur in 
isolated cases and cause interference.

For diagnostic purposes, the T4 findings should always be assessed in 
conjunction with the patient's medical history, clinical examination 
and other findings.