Thyroid nodule diagnosis: A comparative analysis of ultrasonography and fine-needle aspiration cytology

INTRODUCTION

Thyroid nodules (TNs) are abnormal growths in thyroid cells that can form solid, fluid-filled, or mixed masses within the thyroid gland.^[1-3] They are quite common, with a prevalence ranging from 20% to 76% in the population.^[4] Studies have shown that the occurrence of TNs ranges from 2% to 6% through palpation, 19–35% with ultrasonography (USG), and 8–65% based on autopsy findings.^[5] The incidence of TNs is more frequent in females compared to males and rises with increasing age.^[4]

TNs, common growths or lumps, develop within the front of the neck in the thyroid gland.^[6-8] TN prevalence is increasing due to factors such as heightened awareness, improved diagnostic techniques, and widespread use of imaging, particularly ultrasound (US).^[7-9] While most nodules are usually benign (non-cancerous), there is a fraction of nodules that can potentially be malignant (cancerous).^[10,11] This is why it is important to have an accurate and timely diagnosis to determine the nature of the nodule and to plan appropriate treatment, if necessary.^[12] As thyroid cancer rates rise globally, the importance of effective diagnostic approaches becomes paramount to ensure early detection and appropriate management.^[13,14]

USG, a non-invasive imaging technique using sound waves, plays a crucial role in diagnosing and monitoring medical conditions, including the evaluation of TNs. It allows for a detailed examination of nodules, assessing their size, shape, and internal characteristics.^[15-21] In contrast, fine-needle aspiration cytology (FNAC) is a medical procedure employed for evaluating TNs.^[11,22] Using a thin needle, FNAC extracts a small sample of cells from the TN under US guidance to ensure precision.^[23,24] The extracted sample undergoes cytological examination by a pathologist to study cellular structure and characteristics.^[25,26]

This study compares two methods for diagnosing TNs in Yemen: US and FNAC. It aims to identify potential differences in diagnostic practices and outcomes across public and private hospitals, considering resource disparities. The findings aim to improve TN diagnosis in Yemen, leading to better health outcomes.

MATERIALS AND METHODS

RESULTS

According to the age distribution, the average age of participants was 39.96 years, with a standard deviation of 12.90. The participants were divided into four age groups, with the largest group being 30–45 years (46.8%). According to the gender distribution, 85.1% of participants are female, while 14.9% are male.

DISCUSSION

Identification of TNs has been recommended using a variety of diagnostic techniques, primarily to rule out thyroid cancer. B-mode US is a vital diagnostic imaging method in the evaluation of TN before surgery.^[2] However, the established reference standard for TN evaluation continues to be FNAC.^[29] In this study, we compared the detection and classification of TNs using US results and results from FNAC. Along with measuring diagnostic accuracy, our analysis also looked at sample and nodule characteristics and the relationship between US and FNAC diagnoses.

Regarding the sample characteristics, our findings revealed that the average age of the participants was 39.96 (±12.90). This results are consistent with Alshoabi and Binnuhaid, Cesur et al., and Ram et al., who reported the mean age of 41.2 ± 15, 43.2 ± 9.4, and 43 ± 13, respectively.^[4,30,31] The distribution of participants across age groups showed a larger proportion in the 30–45 years group (46.8%) followed by the 16–29 years group (25.5%). The majority of participants were female (85.1%), while males accounted for 14.9%. This finding is in line with Ebrahim et al. and Ram et al. who reported that 80% of the cases are female.^[6,31]

The association between US results and FNAC diagnoses was investigated to assess the relationship between these two diagnostic modalities. The Chi-square test results indicated a significant association between the US final result and the FNAC diagnoses (χ² = 34.914, P < 0.001). This finding is also reported by Dev et al., who concluded that the US features are associated with FNAC results.^[32] Adding to that, this finding was confirmed by Kumar et al., who concluded that USG is a sensitive modality in the assessment of thyroid swellings with good accuracy.^[33] Further, the finding is consistent with those of Salman et al. who reported that US is an effective method in diagnosing TNs and it can reduce the role of FNAC.^[2]

The size of the nodules showed a significant association between US and FNAC. TNs larger than 1 cm showed an association between US and FNAC results. However, TNs smaller than 1 cm showed no established correlation. This finding is supported by what was stated by Tamhane and Gharib who reported that nodules smaller than 1 cm do not entail undergoing FNAC.^[34] The same finding was reported by Ebrahim et al. who stated that no association between nodule size and FNAC results.^[6]

To further evaluate the diagnostic performance of US compared to FNAC, we analyzed the diagnostic accuracy measures. The sensitivity of the US results was found to be 88.68%, indicating that a high proportion of true-positive cases were correctly identified. This finding is somehow different from that of Salman et al., De et al., and Osseis et al. who reported that US had a sensitivity of 73.9%.^[2,15,35] The specificity value of 70.73% suggests that the US results correctly identified a moderate proportion of true-negative cases. This finding is consistent with that of Salman et al., Alshoabi and Binnuhaid, and Kaur et al.^[2,4,36]

CONCLUSION

Our study demonstrates that US results have a relatively accurate performance in detecting and classifying TNs when compared to FNAC. The significant association between US results and FNAC diagnoses highlights the potential of US as a valuable diagnostic tool for TNs. Future research and larger-scale studies are warranted to validate these findings and further explore the diagnostic utility of US in TN evaluation.

The reliability of US for assessing TNs is a topic that shows significant variation in the literature. Some studies and the general consensus suggest that US alone is not sufficient to diagnose TNs and should be used in conjunction with FNAC. Conversely, other studies propose that advancements in US quality and techniques have improved its accuracy and made it comparable to FNAC. As imaging techniques continue to develop, US scans are expected to become increasingly reliable. Specialized radiology centers with modern equipment and expertise may soon achieve results comparable to FNAC without the need for invasive procedures. Therefore, it is recommended to conduct large studies in these centers to assess and compare the reliability of modern US scans in diagnosing TNs against the current gold standard of FNAC. Future research studies are required to compare the results of the two modalities using updated US modalities.

Potential limitations of the study may include the retrospective nature of data collection, which may result in missing information or incomplete records. In addition, variations in the expertise and experience of healthcare professionals performing USG and FNAC across different hospitals could influence diagnostic accuracy.

Future research directions are suggested to conduct prospective studies comparing the diagnostic accuracy of modern US modalities (such as high-resolution US, elastography, or contrast-enhanced US) with FNAC in the assessment of TNs. This will help validate the potential improvements in reliability that is expected with advancements in US technology.