DIAGNOSTIC RELIABILITY OF BLIND FNAC AND ULTRASOUND GUIDED FNAC USING HISTOPATHOLOGICAL DIAGNOSIS AS THE GOLD STANDARD

Baba iqbal khaliq 1 , Bilal ahmad sheikh 2 , baba aijaz khaliq 3 , omar sharif kirmani 4 and farzana manzoor 5 . 1. Senior resident department of pathology. 2. Proffesor department of pathology. 3. Senior resident department of ent. 4. Associate proffesor department of radiodiagnosis. 5. Post graduate department of pathology goverenment medical college srinagar kashmir 190010. ...................................................................................................................... Manuscript Info Abstract ......................... ........................................................................ Manuscript History


Introduction:-
Thyroid nodules represent a common problem in ent & hns, with an estimated prevalence of 4-7% in the adult population for palpable nodules. The prevalence is higher in women (5%) than in men (1%) 1 . The prevalence of nodules found during autopsies, operations or ultrasound examinations is considerably higher and increases with age [2][3][4] . The majority of nodules are benign. Cancer can be present in 3-10% of nodules, depending on age, gender, radiation exposure, family history, and other factors 5 . Over the last few years, many advances have been achieved in diagnosing thyroid nodules. In addition, various clinical and radiological features have been studied to increase detection rate of differentiated thyroid carcinoma. Unfortunately, these features lack specificity and sensitivity [6][7][8][9] , and none have been so far recommended for a routine use 10 fnac has been established as the first line diagnostic test for thyroid lesions and has proven to be the most valuable modality for preoperative distinction of benign from malignant nodules and to confirm the diagnosis 11 . The accuracy of fnac and the inadequacy rates are influenced by operator technique, experience and the reliability of inserting the needle into the area of interest particularly in cystic nodules. Ultrasound guided fnac has the potential to reduce inadequacy rates, to facilitate accurate targeting of the lesion, to sample the part most likely to yield diagnostic material and to sample the solid portion of cystic nodules which are too small for palpation 12 . Recently, using ultrasound guided fnac increased the sensitivity ranging from 65% to 98%, whereas; the specificity ranges from 72% to 100%, with overall accuracy for cytological diagnosis approaches 95% [13][14][15][16][17][18] . This study was done to compare the results of blind v/s ultrasound-guided fnac in cases of thyroid swellings keeping histopathology as gold standard

Methods:-
This study was conducted in department of pathology government medical college srinagar in collaboration with department of entand department of radiodiagnosis government medical college srinagar kashmir from august 2014 to february 2017. Patients presenting with thyroid swelling were subjected to blind fnac followed by ultrasound guided fnac after taking proper consent. Only those patients who subsequently underwent surgery were included in the study and those in whom surgery was not done were excluded from study. Total 100 patients were included in study. After taking informed consent in local language all patients with thyroid swelling underwent blind fnac followed by ultrasound guided fnac and subsequently underwent surgery and histopathological examination of specimen was done and subsequently compared with fnac findings (both blind as well as usg guided).

Results:-
The 100 patients included in this study who underwent surgery for thyroid swelling following blind and ultrasound guided fnac were studied and the following observations weres made. The age of patients ranged from 11 to 68 years(table 1). The male : female ratio was 1 : 4. Durations of symptoms ranged from 1 month to 3 years. At the time of surgery all patients were euthyroid. During blind fnac 15 cases showed nondiagnostic or unsatisfactory results (tbsrtc category i) in 65 cases lesions were benign and 20 cases were diagnosed as malignant (table 2)ultrasound guided fnac revealed benign pathology in 62 cases and malignant pathology in 38 cases (table  3).postoperatively on histopathological examination 57 patients had benign pathology and 43 patients had malignancy (table 4). As compared to histopathology blind fnac showed 91.48% sensitivity, 87.7% specificity , positive predictive value of 84.31% and negative predective value of 93.4% (table 5),while as compared to histopathology results ultrasound guided fnac showed sensitivity of 97.7%,specificity of 92%,positive predictive value of 89.58% and negative predictive value of 98.27% respectively(table 6a and 6b)

Discussion:-
The importance of fnac investigation in the diagnosis of thyroid tumors has been well established as this is a safe and cost effective and diagnostic procedure; the cost of fnac is minimal, equipment is inexpensive and the technique is simple and results are available in short time 19,20 . Fnac is a well established method and its reliability depends on several factors, such as the skill of the physician or the experience of the cytopathologist. Use of ultrasonography in fnac increases significantly the sensitivity, specificity and accuracy compared with conventional palpation-guided fnac 17 .
In our study, it was observed that majority of patients presented between age group of 21 to 40 years with mean age 0f 34 years. Youngest patient was 11 years old boy and eldest was 65 years old male. This was similar to m. Aggarwal etal who had mean age of 36.5 years and rd bapat etal who had median age of 35 years. Most studies report the majority of the patients with thyroid swellings to be females. In this study also we observed that the major bulk of patients were females. In our study 80% patients were female and 20% were male with female :male ratio of 286 4:1. In a study conducted by m .aggarwal etal they found 46 (83.6%) females and 9(16.4%) males. Safirulla et al in their study also observed that 90% of the patients were females and males comprised of only 10%. In our study on blind fnac of thyroid swelling in 15 (15%)cases sample obtained was inadequate; in 54 (54%)cases lesions were benign and 20 (20%) cases were malignant. On usg guided fnac 64 (64%) patients had benign pathology , 29 (29%) patients had malignant disease. Mundasad b et al reported that fnac analysis revealed 13.88% nonneoplastic, 65.27% neoplastic and 4.16% suspicious aspirates, 13.88% samples were inadequate and 2.77% samples were indeterminate. The inadequate (non-diagnostic) sampling rate of 15% was similar to 14.55% by m aggarwal etal, 19 % rates reported by cai et al and 14% by guhamallick. In our study the sensitivity and specificity of blind fnac and usg guided fnac in predicting thyroid malignancies was 91.48%, 87.7% and 97.7% , 92% respectively. This was similar to that of m. Aggarwal etal, . The positive predictive value and negative predictive for blind fnac and ultrasound guided fnac with histopathology as the gold standard was 84.31%, 93.4%; and 85.58% , 98.27% respectively were found to be almost similar to studies by m aggarwal etal.these findings were also similar to the findings of the study conducted by moon h et al who reported that ultrasound guided fnac has a high diagnostic accuracy with the sensitivity and specificity of 65% to 98% and 72% to 100% respectively. Ogawa y et al in their retrospective study of 1012 samples from 806 thyroid nodules by usg guided method reported that the accuracy of fnac as 75 % and the rate of indeterminate diagnosis as 16 %. The false negative rate was 13 % and the positive malignancy rate was 99 %.  Table 6a and 6b showing sensitivity, specificity ppv and npv of usg guided fnac as compared to hpe.