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Sadaf A. Farooqi , MD

When Laboratory Testing Turns Against Us : Human Anti-Mouse Antibody (HAMA) Interference with TSH and PTH Assays. Sadaf A. Farooqi , MD. Disclosure. No conflict of interest for the authors Sadaf Farooqi , MD Justin Moore, MD Rami Mortada , MD

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Sadaf A. Farooqi , MD

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  1. When Laboratory Testing Turns Against Us:Human Anti-Mouse Antibody (HAMA) Interference with TSH and PTH Assays Sadaf A. Farooqi, MD

  2. Disclosure No conflict of interest for the authors • SadafFarooqi, MD • Justin Moore, MD • RamiMortada, MD • No financial incentives are involved in this presentation

  3. Introduction • Heterophile antibodies, like Human Anti-Mouse Antibody (HAMA) can lead to falsely elevated levels of TSH and PTH • This occurs in specific “sandwich” immunoassays, leading to expensive investigations and unnecessary treatments

  4. Case Presentation Case 1 • 24 yr. old ♀ with Hashimoto’s disease • Wide fluctuation in her TSH levels (76 to 276 mU/L) normal 0.5-5.0mU/L • Multiple escalations of her thyroid hormone dosage lead to a hospitalization for tachycardia • HAMA - 600ng/ml • Levothyroxine replacement was reduced to a weight-based dose (~1.6 mcg/kg/day) • Free Thyroxine level was used for subsequent dose adjustment

  5. Case 2 • 78 yr. old ♀with CKD presented with secondary hyperparathyroidism and widely labile PTH levels over one year (60-899 pg/ml; normal 10-65 pg/ml) • Serum Calcium and vitamin D levels unremarkable • Negative extensive evaluation, including a negative Sestamibi scan • HAMA titer 800ng/ml • Placed on activated vitamin D commensurate with her level of renal function • Subsequently felt well and no further workup or management was undertaken

  6. Human Anti-Mouse Antibodies • Most commonly encountered Heterophile Antibody • 10% of the population may have HAMA which can interfere with immunoassays results

  7. Hetrophile Antibodies HETROPHILE ANTIBODY

  8. Monoclonal Antibodies

  9. Human Anti-Mouse Antibodies • HAMA have broad reactivity with antibodies of other animal species which are often source of assays antibody • They can create both false positive and false negative results

  10. “Sandwich” Assay True Positive

  11. False Positive From Interfering HeterophileAntibody LABEL ANTIBODY NO ANYLATE CAPTURE ANTIBODY HETEROHILE ANTIBODY

  12. Other Tests Affected By Heterophile Antibodies • Tumor markers: CA 19-9, CEA, AFP • PSA • Troponin I • HCG • Hepatitis • Drug levels

  13. Neutralizing The Effect Of HAMA Strategies • Repeat test with different assay • HAMA/Heterophile blocking reagents • Serial dilutions • Nonspecific antibody-blocking tubes • Some commercial kits detect HAMA-positive patient samples

  14. What Should A Clinician Do? • Consider HeterophileAntibody interference if there is a discrepancy between clinical presentation and laboratory values • Clinicians should be aware of this type of interference in routine immunoassays • Document exposureto drugs and screen patients

  15. What Clinical Labs Should Do? • Identify samples-dilution, blocking studies • HAMA assays • Encourage manufactures to make more effective blockers • Communicate with physicians the limitations of methodology

  16. References Baskin HJ, Cobin RH, Duick DS, et al. AACE thyroid guidelines. EndocrPract 2002;8:457-69. Sapin R, Agin A, Gasser F. Misleading high thyrotropin results obtained with a two-site immunometric assay involving a chimeric antibody. ClinChem 2004;50:946-8. Baskin H J, Cobin R H, Duick D S. et al AACE thyroid guidelines. EndocrPract 2002. 8457–469.469. Hollowell J G, Staehling N W, Flanders W D. et al Serum TSH, T4 and thyroid antibodies in the United States population(1988–1994): National Health and Examination Survey (NHANES 3). J ClinEndocrinolMetab 2002. 87489–499.499.  Cooper D S. Clinical practice: subclinical hypothyroidism. N Engl J Med 2001. 345260–265.265.

  17. Questions?

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