Natural killer (NK) cell count has been studied in relation to a variety of conditions, including cancer, HIV, leukemia, chronic fatigue syndrome, infections and other diseases. One area of interest, the relationship between NK cells and reproductive failure is a controversial area in reproductive medicine. Vaquero et al. conducted a study to propose a set of tests to clarify the diagnosis of repeated implantation failure in patients undergoing in vitro fertilization (IVF); they concluded that thyroid abnormalities, antiphospholipid antibodies, and increased NK levels are more prevalent in women experiencing IVF failure. However, regarding NK cells and reproductive failure, Rai et al. contend that there is no scientific basis for NK testing in routine practice, and the use of immunosuppressant agents based on the results of such testing may be potentially harmful. Ghazeeri and Kutteh noted that the roles alloimmunity and autoimmunity may play in reproductive failure, including recurrent pregnancy loss and failed IVF, have not been clearly established, and they concluded that large, well-constructed studies examining the benefit of immunological evaluation and treatment are needed before definite recommendations can be made.
Tratkiewicz and Szer studied the loss of NK activity as an indicator of relapse in acute leukemia. They concluded that there was a marked reduction in NK activity in patients with active leukemia when compared with healthy controls, and that NK activity substantially improved in complete remission. All patients who relapsed had significantly reduced NK activity, which in some significantly preceded the time of relapse. Their data suggest that regular assessment of NK activity may be a useful diagnostic tool in patients with acute leukemia.
NK cells are a promising area of immunology and cancer research. Experiments are being done on mice to learn how NK cells cause the immune system to respond to cancer cells. Also, Iwao et al. studied the prognostic value of NK cell infiltration in resected pulmonary adenocarcinoma, and concluded that NK cell infiltration may contribute to regulation of tumor progression, and can serve as a useful prognostic marker in overall and stage I pulmonary adenocarcinoma.
NK cell activity has been evaluated for a variety of other prognostic and diagnostic uses. El-Sameea et al. evaluated NK cells as diagnostic markers of early onset neonatal sepsis; they reported that their data raised the possibility that adding NK cell activity to the standard workup of critically ill patients with suspected sepsis could increase the diagnostic certainty and generate improved patient management. Zeman et al. studied the prognostic value of NK cells in monitoring the course of IFN-alpha (Interferon-alpha) therapy in children with chronic hepatitis and concluded that increased NK cells in these children may be determinant of IFN therapy. Researchers at the University of Miami reported that preliminary evidence suggests that measuring NK activity may support identification of chronic fatigue syndrome in a subgroup of patients with more severe symptoms. Researchers at the Mayo Clinic in Rochester, Minnesota are devising a way to manipulate NK cells to destroy cells containing HIV virus (“latent” or “resting” cells). While their experiments have been successful in laboratory test tubes, they have not been tested on patients in clinical trials.
While measurement of NK cells may support certain diagnoses or conditions, specific studies are scattered, small, and inconclusive. Therefore, measurement of NK cells is not supported by evidence in the peer-reviewed medical literature that permits conclusions on the effect of NK cell measurement on health outcomes, or that demonstrates an improvement in net health outcome through use of NK cell measurement.
A literature search of online and MedLine database was performed through August 2008. No articles were identified that would change the coverage position of this medical policy.
A literature search was performed through August 2010. No articles were identified that would change the coverage position of this medical policy.
A search of peer reviewed literature through September 2013 identified no new clinical trial publications or any additional information that would change the coverage position of this medical policy (15-18).
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