Seventeen studies of 1,385 groins, plus 20 patients in which number of groins studied were not specified, were included in the review. Three studies had two subgroups of patients which were considered as separate studies. Including the subgroups, 18 studies were used for the detection rate analysis and 19 studies were included in the analysis of sensitivity. Eight studies reported consecutive patient inclusion 15 studies included an appropriate spectrum of patients. Fourteen studies described the tests and only three studies reported numbers of patients lost to follow-up. Where reported, the duration of follow-up ranged from one month to 95 months.
The detection rate was 88.3% (95% CI 81.9 to 92.6) with statistically significant heterogeneity (Ι²=83.95%, p<0.0001). The subgroup analysis of studies that used blue dye and radiotracers for sentinel lymph node mapping using one method had detection rates of 90.1% (95% CI 71.3 to 92.9) versus using one method (85.1, 95% CI 1.3 to 92.9).
The pooled sensitivity was 88% (95% CI 83-92% with significant statistical heterogeneity (Ι²=42%, p=0.0285).
Subgroup analysis of the mapping method showed a pooled sensitivity of 60% (95% CI 15 to 95) for blue dye alone and 84% (95% CI 72 to 92) when radiotracer was used alone. Sensitivity was 90% (95% CI 85 to 95) when both methods were used. In another analysis where two studies of patients with palpable inguinal nodes were excluded, pooled sensitivity was 90% 95% CI 85 to 94). The pooled sensitivity of studies using radiotracer and blue dye for sentinel lymph node mapping and recruiting patients with node-negative disease was 92% (95% CI 86 to 96). The pooled sensitivity of two studies where inguinal ultrasonography was used to detect suspicious inguinal lymph nodes was 93% (95% CI 85 to 97).
There was no evidence of publication bias found for any of the outcomes, although the reviewers acknowledged the limitations of the tests because of low power, particularly for detection rates.