Recently, many comparative studies have aimed to clarify which needle size is more suitable for diagnosing solid pancreatic masses, especially in the comparison of 22-G and 25-G needles. Published data on the sensitivity of EUS-FNA for detecting pancreatic masses have varied. Some authors concluded that a larger diameter needle has the advantage of acquiring more tissue than a smaller-diameter needle.[24–26] Indeed, this advantage may have a beneficial diagnostic effect in the use of diagnosis by 22-G needles for histology and immunohistochemistry examinations. However, the score of ease of puncture by the 25-G needle was significantly higher than that of the 22-G needle. A limitation of these studies was the relatively small number of patients with pancreatic lesions that lack the statistical power to make a clear statement regarding the utility of needle size.
A meta-analysis, such as that performed in this study, is a potentially useful tool in this situation because pooling data can create very powerful results compared to the data obtained from smaller individual studies. To our knowledge, our study is the first meta-analysis to include a pooled analysis of prospective controlled trials comparing the 22-G and 25-G needles with regard to operating characteristics and diagnostic yield in EUS-guided sampling of pancreatic masses. Our review provides a comprehensive summation of the current literature describing the sensitivity and specificity of 22-G and 25-G needles in EUS-FNA for the diagnosis of solid pancreatic masses. For this study, attempts were made wherever possible to closely follow the Cochrane Collaboration recommendations. We prespecified a rigorous study protocol and searched several electronic databases, identified international conference abstracts, and searched the study reference lists for relevant trials without language restrictions.
The search yielded 2811 original citations, of which 11 studies with 837 patients were eligible for the review. The 22-G needle size was used for a total of 412 patients and resulted in a pooled sensitivity of 88% (range, 84–91%) and specificity of 100% (95–100%). The 25-G needle size was used for a total of 425 patients and resulted in pooled sensitivity and specificity of 92% (range, 89–95) and 100% (range, 94–100%), respectively.
We also used both PLR and NLR as our measures of diagnostic accuracy since they can be more easily interpreted and applied to clinical practice. The PLR is a measure of how well the diagnosis identified the malignant pancreatic mass, whereas the NLR assesses how well the same diagnosis excludes the disease. Likelihood ratios >10 and <0.1 provide strong evidence to include or exclude a diagnosis, respectively. According to our analysis, the PLR and NLR were 12.61 (5.65–28.14) and 0.16 (0.1–0.21) for the 22-G needle and 8.44 (3.87–18.42), and 0.13 (0.09–0.18) for the 25-G needle, respectively. SROC curves were drawn to see any heterogeneity between studies and an AUC of 1 for any test indicates that the test is excellent. The AUC value was 0.97 for the 22-G and 25-G needles. Compared to the study of 22-G EUS-FNA needles, our study showed that 25-G needles have superior sensitivity for solid pancreatic mass EUS-FNA. The pooled results from this analysis are consistent with the trend from previous studies, which lack the statistical power to make a clear statement regarding selection of the most adequate needles for EUS-FNA. The reason for the observed superior diagnostic accuracy of the 25-G needle in this analysis is uncertain. One possible reason is that the smaller 25-G needle might provide less bloody and contaminated specimens and more easily penetrate a calcified or hard mass. Needle size selection is, in practice, a complex process. For instance, whether the lesion is solid or cystic may influence the endosonographer's decision to use a particular needle size.
The present study has several limitations. First, it had a small sample size. However, we contacted each author to supplement the missing data. Second, only English-language studies were included from this analysis. If the search had been extended to include literature published in other languages, it is possible that additional relevant trials may have been identified. Additionally, any other factor would influence the result of the meta-analysis such as the baseline characteristics of the patients (including age, sex, pathologic stage, lesion location).
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