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Fecal immunochemical testing (FIT) had good diagnostic accuracy for colorectal cancer (CRC) but only moderate accuracy for advanced neoplasia in high-risk patients, authors of a meta-analysis concluded.

FIT compiled an average sensitivity and specificity for CRC exceeding 90% in 12 clinical studies included in the analysis. Sensitivity for advanced neoplasia dipped to less than 50%, although specificity again exceeded 90%, according to Anastasia Katsoula, MD, of Hippokration General Hospital in Thessaloniki, Greece, and colleagues.

The authors acknowledged that wide confidence intervals, especially for sensitivity results, raised legitimate questions about the findings, as reported online in .

"Further research with rigorous diagnostic accuracy studies and randomized clinical trials is warranted to assess the full effectiveness of FIT implementation as a means to promote more individualized and more flexible alternative screening options in patients at higher risk of CRC, based on their own values and preferences,"

The author of an noted an absence of randomized clinical trials with long-term outcome data to inform decision-making about screening individuals at high risk of CRC.

"Until such results are available, the evidence for the efficacy of any screening strategy in such populations can only be indirectly inferred through observational studies and assessments of the diagnostic accuracy of each test, bearing in mind the higher-than-average baseline prevalence of CRC and adenomas and the higher-than-average lifetime risk of CRC," wrote Grigorios I. Leontiadis, MD, PhD, of McMaster University in Hamilton, Ontario.

Despite acknowledged limitations of the analysis, some useful inferences can still be made, Leontiadis add. Because FIT demonstrated good diagnostic accuracy for CRC but unsatisfactory accuracy for advanced neoplasia, "FIT as a triage test would be adequately accurate for secondary prevention but not for primary prevention of CRC in this [high-risk] population."

According to the data presented, of every 1,000 high-risk individuals tested, 102 will have advanced neoplasia and eight will have CRC. "FIT will correctly identify seven of eight individuals with CRC but miss most of the individuals with noncancerous advanced neoplasia (52 of 94), preventing them from having colonoscopy. The absolute numbers of missed noncancerous advanced neoplasia are probably too large to justify using FIT as a triage test in people with family or personal history of CRC or adenomas."

Guidelines for early detection of CRC in average-risk patients support use of several screening modalities, including fecal occult blood tests, colonoscopy, and CT colonography. Recommendations for higher-risk patients support only colonoscopy, a strategy associated with higher cost, lower adherence, and an increased risk of rare but potentially serious complications, Katsoula's group noted.

Over the past decade, results of several clinical studies made a case for using FIT as a screening modality for higher-risk patients. However, the support for FIT came from extrapolation of data obtained primarily in populations with an average risk of CRC. To evaluate FIT's potential use to screen higher-risk patients, Katsoula's group performed a systematic review and meta-analysis of published studies involving asymptomatic individuals with a family or personal history of CRC.

The 12 studies selected for the analysis comprised a cumulative total of 6,204 participants. One study was a randomized trial, and the remaining 11 were cross-sectional studies. The authors judged seven studies as having a high or unclear risk of bias. All 12 studies used colonoscopy as the reference standard for comparison of FIT's diagnostic performance.

All of the studies evaluated FIT for detection of advanced neoplasia, and seven (n=4,790) included data specifically for CRC. The prevalence of advanced neoplasia ranged from 3.2% to 14.5% across the studies and the prevalence of CRC from 0.6% to 2.1%. Across the studies, FIT sensitivity for CRC ranged from 0.25 to 1.00 and specificity from 0.87 to 0.95. Pooled estimates yielded a sensitivity of 93% for sensitivity and 91% for specificity.

Sensitivity and specificity for detection of advanced neoplasia ranged from 0.29 to 0.83 and from 0.85 to 0.98. Pooled data yielded estimates of 48% for sensitivity and 93% for specificity.

The authors performed a separate pooled analysis of five studies considered at low risk of bias. That analysis yielded a sensitivity for CRC of 97% and specificity of 91%. Sensitivity and specificity for advanced neoplasia were 44% and 94%.

The authors also analyzed studies that included data only from patients with a family history of CRC, producing a pooled sensitivity of 86% and specificity of 91% for CRC detection and sensitivity of 44% and specificity 94% for advanced neoplasia.

An analysis that excluded studies that delayed colonoscopy for patients with negative FIT results yielded a sensitivity of 97% and specificity of 91%. Values for advanced neoplasia were 46% and 93% for sensitivity and specificity, respectively.