Valutazione del cut-off della tireoglobuina in linfonodi laterocervicali, con strumento LIAISON XL- DiaSorin

Diagnostic value of tireoglobulin cut-off in cervical lymph node, with LIAISON® XL – DiaSorin Introduction.Fine needle aspiration cytology (FNAC) and the measurement of thyroglobulin (Tg) in needle washout (FNA-Tg) have been recommended to identify LN (lymph node) metastases from PTC (papillary thyroid cancer), particularly in the case of very small cervical LNs. In fact, Tg is produced only by follicular cells, and its detection in non thyroidal tissues facilitates the diagnosis of persistence, recurrence, or metastasis of PTC. There is still some controversy regarding the cut-off value and the influential factors of thyroglobulin concentration in washout fluid from FNAC. Aims.Our aim was to validate the cut-off value of FNA-Tg in diagnosing malignant LNs with LIAISON® XL (DiaSorin) automated chemiluminescence method. We used standard citology and we tried to investigate the influential factors that could determ the discrepancy between the final diagnosis and FNA-Tg. Material and Methods. We conducted a retrospective study based on Sant’Andrea hospital records with 124 cases of FNA-Tg measurement from 89 patients. FNAC was evaluated by the conventional method: the aspirates were immediately smeared on slides, treated immediately with Cytofix (BiOptica) and processed using Papanicolaou stain. The same needle and syringe were rinsed with 1 ml of normal saline, and the washout fluid was submitted for FNA-Tg measurement. FNA-Tg cut-off levels were determined by ROC curve. Result. All the LNs analyzed referred to patients with suspected thyroid neoplasia or with possible resumption of disease. 41 patients had been thyroidectomized (47%), while the other 48 had thyroid. 124 lymphnodes were studied, 57 were cytologically positive, while 67 LNs were negative. Three ROC curves were obtained, the first included all patients. The cut-off value was 16.05 ng / mL with aspecificity of 97.10% and a sensitivity of 94.55%. The reference value of our Tg method was 0.2-70.0 ng / mL. This value was confirmed in the second ROC curve only for patients who had not undergone thyroidectomy, in fact the value obtained was 16.05 ng / ml, with a specificity of 100% and a sensitivity of 96.55%. The third ROC curve, which was calculated with data from thyroidectomized patients, showed a lower cut-off value: 5.54 ng / mL, with a specificity of 95% and a sensitivity of 96.15%. These values are in line with the values reported in the literature which points out that in patients who have undergone thyroidectomy, the cut-off is lower. The Tg values obtained from the examinationof washing liquid were statistically evaluated. Range and median were calculated. We performed the ROC curveanalysis to estimate the FNA-Tg cut-off value. Our value of FNA-Tg cut-off was 16.05 ng / mL in non-thyroidectomized patients,while it was 5.54 ng / mL in thyroidectomized patients. Conclusion.Measurement of Tg in needle aspirationassociated with FNAC shows excellent diagnostic performance in LN and high specificity and sensitivity in the early detection of nodal metastases sonographically with suspect of PTC. Our study allowed the definition of a cut-off using the LIAISON® XL, which in the literature seems not to have been studied for FNA Tg. We also showed that these values are markedly different between thyroidectomized and non-thyroidectomized subjects confirming that FNA Tg associated with FNAC can be used for the screening of metastatic LN in thyroidectomized patients and in not thyroidectomized patients, positive or not for PTC. The use of differentiated cut-offs is recommended.

Il carcinoma della tiroide è la più frequente neoplasia del sistema endocrino (90% circa dei casi) e rappresenta circa il 3,8% di tutte le neoplasie. Nelle ultime decadi la sua incidenza è progressivamente aumentata in quasi tutti i Paesi. La mortalità per carcinoma tiroideo non ha mostrato un parallelo incremento, perché l’aumentata incidenza è da attribuirsi quasi esclusivamente ai piccoli carcinomi papillari che hanno una prognosi nettamente più favorevole degli altri istotipi. La misurazione della tireoglobulina (Tg) nel lavaggio dell'agoaspirato è spesso usata per aumentare la sensibilità della FNAC (Fine Needle Aspiration Cytology) nell'identificazione delle metastasi linfonodali (LN) di carcinoma papillifero tiroideo. Lo scopo di questo studio è l’identificazione del cut-off della tireoglobulina nel liquido di lavaggio dell’agoaspirato di LN laterocervicali. utilizzando lo strumento LIAISON®XL (DiaSorin S.p.A., Saluggia,TO) che utilizza un metodo basato sull’immunochemiluminescenza automatizzata. Da Gennaio 2016 a Dicembre 2017, sono stati presi in considerazione presso l’Ospedale Sant’Andrea di Roma 124 agoaspirati, da pazienti con LN laterocervicali ecograficamente sospetti, eseguiti su linfonodo, ed è stato eseguito il dosaggio della Tg su liquido di lavaggio. Tutti i LN analizzati si riferivano a pazienti con sospetto di neoplasia tiroidea o con possibile ripresa di malattia. Nel nostro studio abbiamo voluto correlare la FNA-Tg con il gold standard della citologia. Sono state costruite 3 curve ROC; la prima comprendeva i dati di tutti i pazienti. Il valore di cut-off ottenuto in questo caso era di 16,05 ng/mL. La seconda curva ROC era costruita solo con i dati dei pazienti che non avevan osubito tiroidectomia, il valore ottenuto (16,05 ng/mL) confermava il valore precedente. La terza curva ROC, calcolata con i dati dei pazienti tiroidectomizzati, mostrava un valore di cut-off molto più basso: 5,54 ng/mL. Questo studio ha dimostrato che i valori di cut off differiscono tra i soggetti tiroidectomizzati e non, confermando che la FNA-Tg associata alla FNAC può essere utilizzata per lo screening dei LN metastatici nei pazienti tiroidectomizzati e nei pazienti non tiroidectomizzati, positivi o meno per la PTC, purché si utilizzino cut-off differenziati.