Test Overview
Test Methodology

Sandwich immunoassay with Heterophile Blocking Tube (HBT) pretreatment

Test Usage

A heterophilic sample is a serum or plasma sample containing antibodies which are able to bind to animal antibodies used in immunochemistry assays. The most commonly reported assay interference effect of heterophilic antibodies is a false positive assay result. The Heterophilic Blocking Tube (HBT) allows for the elimination of false positive heterophilic interference in serum or plasma for sandwich immunoassays (e.g., FSH, LH, Prolactin, TSH, Ferritin, CEA, AFP, BHcG, CKMB, CA125 and CA19-9). HBT is a sample pretreatment/second assay intended to confirm or disqualify the original non pretreatment assay result. If the pretreatment result is the same as the original non treated result, the immunochemistry is not affected by a heterophilic antibody interferent in the patient's sample. If the pretreatment sample is lower than the original result, the sample may contain heterophile antibodies affecting the immunoassay and the original result will not be reported.

Reference Range *

No heterophilic antibody interference detected.

* Reference ranges may change over time. Please refer to the original patient report when evaluating results.

Test Limitations

For diagnostic purposes, the results obtained by this sample treatment should be used in addition to other data available to clinicians. There may be some samples with extremely strong heterophilic interference; in these cases, the blocking tube may not be able to block all of the assay interference.

Test Details
Days Set Up
Monday - Friday
Analytic Time

8 hours

MiChart Code
  • HAMA
  • Heterophile AB Interferent Scr
  • Heterophile Interference Screen
  • Heterophile Ab
  • Heterophilic Antibody
  • Heterophile Antibody Screen
  • Heterophilic Blocking Tube (HBT)
Chemical Pathology
Specimen Requirements

Collect specimen in an SST (preferred), red top, green top, or lavender top tube. A sandwich immunochemistry assay must be requested on the sample to perform Heterophile Antibody Interferent testing.

Alternate Specimen
Red top, Green top, or Lavender top acceptable.
Normal Volume
1 mL serum or plasma
Minimum Volume
0.5 mL serum or plasma
Additional Information

Heterophile antibody interferent screening will be performed at no charge by client or clinician request for specific UMHS performed immunoassays. Sandwich immunoassay testing must be performed by the UMHS Chemical Pathology Laboratory.