Title: A ‘cut off’ value of ‘AP measurement to Transverse measurement Ratio (A/T Ratio)’ for a provisional diagnosis of malignancy in sonologically confirmed solitary nodules of the thyroid
Authors: N.J. John, S. Mangalanandan, K.K. Raishad Khan, S. Beenamol
Introduction: The low accuracy of ultrasound features for diagnosing malignancyin the thyroid justifies the widespread use of FNAC on sonologically selected nodules. The sonographic feature, ‘height more than width’or in other words‘ anteroposterior measurement by transverse measurement ratio ≥1’ has been studied earlier. No study has attempted to define the ‘cut off’ value of ‘A/T ratio’ that will give the best diagnostic yield in sonography and FNAC of solitary nodules of the thyroid gland and this study is an attempt to define the same.
Aim of the work: (1) To estimate the statistical measures of performance of positivity of the test criterion ‘height (AP diameter) equal to or greater than the width (transverse diameter) to provisionally diagnose malignancy in solitary thyroid nodules. (2) To estimate the ‘cut off’ value of ‘A/T ratio’ that will give the best set of statistical measures of performance.
Patients and Methods: 40 cases of sonologically confirmed solitary nodules were selected. The gray scale sonographic features of the solitary nodules and their three dimensions were noted. The ‘A/T ratio’, i.e., the ratio between anteroposterior measurement and transverse measurement of the nodules was calculated. The A/T ratio was correlated with presence of malignancy on FNAC/Histopathology.
Results: An A/T ratio greater than 0.79 has a sensitivity of 100% and specificity of 70.6% for a presumptive diagnosis of malignancy in sonologically confirmed solitary nodules of the thyroid gland. An ‘A/T ratio equal to or greater than one’ has a sensitivity of 66.67% only and specificity of 85.3%,for a presumptive diagnosis of malignancy in solitary nodules.
Conclusion: The test criterion of A/T ratio equal to or more than 0.79 is much superior to the test criterion, ‘A/T ratio equal to or greater than one’for a sonologic presumptive diagnosis of malignancy in solitary nodules of the thyroid.
Keywords: Solitary thyroid nodule, recruitment for FNAC, A/T ratio, height more than width