On 2017 Mar 20, Prajak Barde commented:

One of the objective of the meta-analysis by Bai B et al is to assess the relationship between human cytomegalovirus and colorectal cancer (CRC) risk. Author analyzed four studies to demonstrate that tumor tissues had a significantly higher rate of HCMV infection (OR = 6.59, 95% CI = 4.48–9.69), thus confirming that CRC tissue is significantly burdened with HCMV DNA as compared to adjacent normal tissues. However, it is not clear how the conclusion of an increased risk of CRC due to HCMV infection is drawn. As detection of HCMV DNA in CRC tissues by itself don’t provide adequate evidence to prove the causal role of HCMV in CRC, further explanation is needed to justify increased risk of CRC due to HCMV infection. In addition, in light of multiple etiological factors responsible for causation of CRC (e.g. insufficient activity, high-fat diets, smoking and living in a developed country)2, the increased risk associated with HCMV in relation to these risk factors also need to be ascertained and established.

There are diagnostic challenges in detecting HCMV, due to “hit and run” mechanism of virus, though author considered PCR technique that showed higher positive rate than In situ hybridization (ISH) and immunohistochemistry (IHC),3 the validity of “negative results” of studies considered for meta-analysis should be ascertained before drawing any conclusion based on these results.

On 2017 Mar 20, Prajak Barde commented:

One of the objective of the meta-analysis by Bai B et al is to assess the relationship between human cytomegalovirus and colorectal cancer (CRC) risk. Author analyzed four studies to demonstrate that tumor tissues had a significantly higher rate of HCMV infection (OR = 6.59, 95% CI = 4.48–9.69), thus confirming that CRC tissue is significantly burdened with HCMV DNA as compared to adjacent normal tissues. However, it is not clear how the conclusion of an increased risk of CRC due to HCMV infection is drawn. As detection of HCMV DNA in CRC tissues by itself don’t provide adequate evidence to prove the causal role of HCMV in CRC, further explanation is needed to justify increased risk of CRC due to HCMV infection. In addition, in light of multiple etiological factors responsible for causation of CRC (e.g. insufficient activity, high-fat diets, smoking and living in a developed country)2, the increased risk associated with HCMV in relation to these risk factors also need to be ascertained and established.

There are diagnostic challenges in detecting HCMV, due to “hit and run” mechanism of virus, though author considered PCR technique that showed higher positive rate than In situ hybridization (ISH) and immunohistochemistry (IHC),3 the validity of “negative results” of studies considered for meta-analysis should be ascertained before drawing any conclusion based on these results.