The role of DAP IV activity testing in the cytological examination of tumors of the «gray zone» TBSRTC IV in the prediction of papillary thyroid cancer and metastases

Abstract

One of the most effective methods of thyroid nodules diagnosis is the fine‑needle aspiration puncture biopsy (FNAPB), allowing evaluation of the cytological characteristics of thyroid tumors. To improve the diagnostic efficiency of cytological investigations, additional methods can be implemented, including cytochemical determination of dipeptidyl aminopeptidase (DAP IV).
 Objective — to analyze and establish the DAP IV activity thresholds, at which the probability of detecting papillary thyroid cancer (PTC) and its metastases in lymph nodes is clinically significant in patients with cytological conclusion of the TBSRTC IV category.
 Materials and methods. For the first time in Ukraine, an analysis was made of the possibility of using DAP IV to predict papillary cancer and its metastases in cases of tumors with TBSRTC IV using ROC analysis to determine the threshold values of DAP IV activity, defining the clinically significant probability of metastases.
 Results. It has been established that 6 is the cut‑off DAP IV value for diagnosis of papillary thyroid cancer, and 8 is the cut‑off point for the presence of its metastatic deposits. Thus, in case of DAP IV activity values between 6 and 8, the probability of papillary thyroid cancer diagnosis and its metastases significantly increases. The prognostic value of a positive result, i.e. obtaining a malignant diagnosis with DAP IV 6 activity, is 85.1%, which can be interpreted as high. With increasing DAP IV activity in patients with TBSRTC IV category, the probability of the reveal of papillary thyroid cancer metastases increases (threshold value of activity for DAP IV metastases 8 with counter sensitivity 0.267).
 Conclusions. The obtained results allow a practitioner to choose treatment options: with values of DAP IV <6, the alternative therapies or active monitoring can be used, and with DAP IV <8, the need for preventive dissection may not be advisory.