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

2. Disclosure No conflict of interest for the authors Sadaf Farooqi, MD
Justin Moore, MD
Rami Mortada, 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
- TSH and PTH are commonly used, no need to explain to what it stands for you can say it in your oral presentation

4. Case Presentation Case 1 24 yr. old ♀ with Hashimoto’s disease
Wide fluctuation in her TSH levels (76 to 276 mU/L) normal mU/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
Decreased wording in the slide
You might want to mention in your oral presentation normal value of TSH
Milli units/liter

5. Case 2
78 yr. old ♀ with CKD presented with secondary hyperparathyroidism and widely labile PTH levels over one year ( pg/ml; normal 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
Decreased wording in the slide
Mention normal PTH values
Mention that Phosphorus was normal
Expect a question if her activated Vit D was checked. Usually by the time the pt requires activated Vit D she might have some element of secodary hyperpara which might be contributing to her elevated PTH

6. Human Anti-Mouse Antibodies
Most commonly encountered Heterophile Antibody
10% of the population may have HAMA which can interfere with immunoassays results
It is now believed, on circumstantial evidence, that these heterophile antibodies are natural antibodies in normal people, although they could also represent autoantibodies

7. Hetrophile Antibodies
ANTIBODY

8. Monoclonal Antibodies
Present in patients receiving immunotherapy with monoclonal antibodies like infliximab
May also be naturally occuring or autoantibodies

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 Heterophile Antibody
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
(Prostrate specific antigen)
(Human chrionic gonadotrophin)

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 Heterophile Antibody 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 exposure to 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. Endocr Pract 2002;8:
Sapin R, Agin A, Gasser F. Misleading high thyrotropin results obtained with a two-site immunometric assay involving a chimeric antibody. Clin Chem 2004;50: Baskin H J, Cobin R H, Duick D S. et al AACE thyroid guidelines. Endocr Pract 2002. 8457–
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 Clin Endocrinol Metab 2002. 87489–  
Cooper D S. Clinical practice: subclinical hypothyroidism. N Engl J Med 2001. 345260–
I’d prefer these in the actual slides if possible, rather than here…

17. Questions?