College of American Pathologists
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CAP Today




October 2009

Heterophilic antibody interference Heterophilic antibody interference

A technical brief by Ellis, et al.,1 and subsequent letter to the editor by Cantor, et al.,2 were published in 2005 showing the usefulness of heterophilic blocking tubes, or HBT, in identifying false-positive specimens, thereby providing an estimate of the incidence of false-positive test results on several analyzers, including the Roche Elecsys and Abbott Architect. The letter to the editor highlighted the need to use a nonmurine blocker for assays that contain an anti-mouse antibody. Beckman uses this design in several of its Access assays (as its package inserts indicate). A nonmurine HBT has been introduced for use in those assays that contain an anti-mouse antibody and are therefore unable to use a murine blocker.

The clinical utility of the nonmurine HBT was demonstrated last year in the Department of Pathology and Laboratory Medicine of NorthShore University Health System. In March 2008, a 35-year-old female with no signs of coronary involvement was tested for total cardiac troponin I on the Beckman Access and the result was 17.0 ng/mL. The patient’s myoglobin, CK-MB, and EKG were normal, but the patient was reported to have “some kind of dermatologic problem.” After treatment with the nonmurine HBT, the result was 1.5 ng/mL. Her physician was satisfied with the result and will monitor her annually.

The “dermatologic problem” was diagnosed as Sweet syndrome,3 which is an acute febrile neutrophilic dermatosis. Sweet syndrome is characterized by fever; leukocytosis; erythematous, well-demarcated papules; and plaque formation showing dense neutrophilic infiltrates. Though Sweet syndrome is relatively rare, about one-third of patients have recurring episodes after being treated successfully with glucocorticoids.

This case demonstrates the need for dialogue between the clinician and laboratory professionals when unexpected results are obtained. Immunoassays have inherent problems with specificity and interference with heterophilic antibodies. Laboratorians need to be aware of the limitations of immunoassays as they relate to disease in which there is immune stimulation.


  1. Ellis J, Livesey JH. Techniques for identifying heterophilic antibody interference are assay specific: study of seven analytes on two automated immunoassay analyzers. Clin Chem. 2005;51:639–641.
  2. Cantor D. Reason for limitations of HBT use on certain Beckman Access assays. Clin Chem. 2005;51:1311.
  3. Joe EK. Sweet syndrome. Dermatol Online J. 2002;9(4):28 (

David Cantor
Scantibodies Laboratory
Santee, Calif.

Robert Rosecrans, PhD
Department of Pathology and Laboratory Medicine
NorthShore University Health System
Highland Park, Ill.

Licensure and interstate diagnosis Licensure and interstate diagnosis

We are writing about the CAP’s policy, “Licensure Requirements for Interstate Diagnosis, Including Interstate Telemedicine Practice” ( Many pathologists have multiple out-of-state licenses based on differing opinions of state laws. We propose that the CAP review aspects of this policy with further consideration of the issues we present here.

The rationale for the CAP’s policy is the “right of each state, through licensure, to regulate the practice of medicine in order to protect the health and welfare of its citizens.” States have this right, but the potentially contentious issues are how the practice of pathology is defined, whether state licensure where one practices pathology is sufficient, whether where the patient presents for clinical diagnosis is relevant to an endpoint pathologist’s licensure, and whether states should attempt to regulate laboratories or pathologists, or both, in another state based on a sample’s state of origin.

It is common for samples to be sent from a physician in one state to a laboratory in another. Typically, neither the decision determining where the sample is sent nor the sample shipment is the responsibility of the endpoint pathologist; it is the parties in the originating state who are responsible. It can be argued the practice of pathology begins once a sample is received by the laboratory where the endpoint pathologist works or has a direct influence on a sample. Saying that the endpoint pathologist is engaged in the interstate practice of pathology because a sample originated in another state is analogous to saying that a physician seeing a patient who originated in another state is engaged in the interstate practice of medicine.

The exemption for referral center pathologists is another issue. These pathologists review material for clinicians at their facility and may disagree with the initial interpretation/diagnosis and provide an entirely different interpretation/diagnosis that significantly affects patient care. Consistency with the state’s rights and patient welfare rationale should compel the CAP to argue that referral center pathologists are not exempt and do need licensure in states where samples originate—though this is not our position.

The CAP’s policy suggests that licensure by the state in which a pathologist practices is insufficient and all laboratories and personnel handling out-of-state specimens should be required to have licensing/certificates from all states where samples may originate. Some states do have laws to this effect. Imagine, however, if all states required this. If we start by considering a group of 10 pathologists and assume a fee of about $400 every two years for 50 states, this would add up to about $100,000 per year plus resources to manage such things as renewals and CME. Now include all other laboratory personnel. Do we really need to add such costs and bureaucracy to our health care system?

It could be argued that licensure of pathologists within the states they actually practice is sufficient. However, we propose that the CAP at least consider a neutral position, possibly recommending that pathologists seek legal counsel with respect to the issues related to the specifics of their practices and the potential issues related to out-of-state licensure.

Ron Lee, MD
Joseph Papiez, MD
Brentwood, Tenn.

Richard R. Gomez, MD, chair of the CAP Federal and State Affairs Committee, replies: The regulation of interstate medical practice differs greatly among all the states; however, it has been the CAP’s position, since 1995, that state licensure of physicians by the state where the specimen is taken from the patient is the most effective mechanism of regulating the practice of medicine. The practice of medicine is defined in state medical practice acts as including “diagnosis” of a patient. Therefore, when a diagnosis is made of a specimen, the pathologist is performing a medical act upon a patient that requires licensure. The transmission of a patient specimen by electronic or by other traditional means should not be construed to sever the nexus between the pathologist and the patient.

Thus, in the CAP’s view, the basis for medical licensure is where the patient presents for diagnosis and the specimen is taken. The CAP strongly believes that the practice of pathology is not a consultant service, unless it is provided as a second opinion on a specimen to another pathologist. In these situations, when a pathologist is providing a consultative service to another pathologist, the CAP believes medical licensure should not be mandated. Accordingly, some medical practice acts exempt from licensure requirements pathology conferrals that are episodic or entail a secondary or tertiary diagnosis, provided to other in-state licensed pathologists who are accepting responsibility for the primary diagnosis.

The CAP’s transformation agenda reinforces and reemphasizes that the pathologist service is a physician service rendered to patients, establishing a clear physician-patient relationship, even when the pathologist may never see the patient and the diagnostic opinion is being submitted to a referring clinician. Many states, following this logic, have opted to regulate the interstate practice of pathology in a manner consistent with the CAP’s position. Moreover, in a highly networked world in which international borders are no barrier to medical practices, it is even more important for states to ensure the integrity and quality of medical care through a state licensure system.

The CAP is greatly concerned about public policy that may devalue or commoditize the practice of pathology, or inappropriately differentiate pathology from other types of physician services in which patients are directly seen and evaluated. For this reason, the inherent attributes of pathology should not be a basis for exemption from state laws that would otherwise require licensure of out-of-state physicians providing services for in-state patients. Lastly, we concur with the authors that every physician considering interstate practice should consult with legal counsel or state medical boards, or both, to determine whether a particular state requires licensure by an out-of-state physician providing services to a patient in that state.

Remote Amazon laboratory Remote Amazon laboratory

I enjoyed reading the February 2009 article about pathologist Arturo Heredia, MD, who practices in Pucallpa, a city of 200,000 in the Amazon jungle basin of eastern Peru (“Jungle favor—remote Amazon lab bolstered by grant”). I was one of the Pathologists Overseas volunteers who covered Dr. Heredia’s practice while the Los Angeles pathologists hosted him. Sofie Alvarez, a local cytotechnologist and former colleague, joined me on the trip.

The general public hospital where we practiced in Pucallpa comprised several midsize buildings that were old but tidy and clean. Our bungalow was about 1,000 square feet and included a pathologist’s office. We arrived laden with donated supplies, including two AO microscopes, one of them double-headed. During my stint it was common to receive 10 to 12 surgical pathology specimens every day, most submitted in plastic bags with an attached requisition. Clinical history and pre-op diagnosis were usually included and were generally adequate and accurate. The most common specimens consisted of skin (leishmaniasis common), gastric and cervical biopsies, uteri, lymph nodes, and gallbladders. Storage space was scant, so we held specimens for only a week. Reports were translated into Spanish by the bilingual secretary and issued by computer. Tissue was processed by hand. The only special stains available were AFB and PAS.

While I worked, Sofie taught several lab employees the basics of screening Pap smears. The students loved learning from her and were eager for every minute of her time. She also screened a six-month backlog of Pap smears. Graduation day came quickly. The parents of the students hosted a wonderful celebration and diplomas were conferred. By the end of our one-month assignment it was difficult to say goodbye.

Dr. Heredia runs a solo surgical pathology operation with limited resources, a difficult but admirable task. Pucallpa residents are warm, welcoming, and grateful for all the help.

Cecilia Carrick, MD
San Diego