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The main finding of the present study was that elevated MPV might indicate malignancy in patients with thyroid nodules. MPV is considered to be associated with certain malignancies. Elevated MPV values have been reported in various types of cancer at the time of diagnosis (13). Another study reports on increased MPV in patients with colon cancer, which was reduced after surgery (11). Increased MPV has also been reported in gastric (10)and epithelial ovarian tumors (14).

We will discuss the rationale for MPV elevation in cancer at this point. Inflammation causes an increase in the levels of circulating cytokines. These cytokines, especially interleukin (IL)-6, may interfere with megakaryopoiesis in bone marrow and cause production of larger platelets. This may be the underlying reason for increased MPV in cancer patients. Cancer is also associated with chronic inflammation, thus such a causal relationship may be present.

Various diagnostic tools are available to differentiate malignant from benign thyroid nodules. Ultrasonography characteristics of malignant thyroid nodules, vertical rather than horizontal shape, spiculated borders, hypoechogenicity and microcalcifications all have about 40%-48% sensitivity in detecting malignancy (15). Leenhardt et al. report on sonography sensitivity and specificity for thyroid nodule malignancy of 75% and 61%, respectively (16).

Cold thyroid nodules on thyroid scintigraphy require further evaluation for suspicious malignancy. However, Kountakis et al. report that only 27.5% of hypofunctional (cold) thyroid nodules were malignant on scintigraphy (17). Although hot nodules in scintigraphy are considered almost always benign (18), malignancy was detected in 6% of hyper functioning hot nodules (17). Diagnostic accuracy of a combination of sonography and scintigraphy is not excellent either. Only about 35% of sonographic solid and scintigraphically cold nodules were reported as malignant by fine needle aspiration cytology (FNAC) (19).

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In our study, the sensitivity and specificity of MPV at a threshold of 8.25 were better than by ultrasound and scintigraphy.

Fine needle aspiration cytology of thyroid nodule, which is considered as the most important method for detecting malignancy in thyroid nodules, has a sensitivity of 91% in selecting malignant nodules (20). However, the rate of false-negative and false-positive results of FNAC can be as high as 11% and 7%, respectively (18). Owing to higher sensitivity and specificity of MPV at 8.25 threshold, we think that it can be used in combination with sonography, scintigraphy and FNAC to establish the nature of thyroid nodules. Such a combination not only increases diagnostic accuracy, but also may improve the cost-effectiveness by reducing repeated expensive techniques (FNAC, etc.) in cases of non-diagnostic test results.

Not only thyroid disease but also metabolic alteration such as obesity, type 2 diabetes mellitus and diabetic nephropathy were associated with MPV levels in hemogram tests (21, 22).

There were several limitations to the present study. First, the retrospective design made our results difficult to interpret. Another limitation was the relatively small study population. Finally, we did not compare sonography, cytology and scintigraphy test results of the study population with MPV, which should be the subject of another study in the near future.

In conclusion, increased MPV should be considered as an assistive diagnostic tool in differentiating malignant and benign thyroid nodules. However, further prospective studies are required to confirm its usefulness in this population.

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About the Author: Tung Chi