— When studies with a moderate or greater risk of bias were removed, survival benefit vanished

by Kristina Fiore


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A close up of a box and blister pack of ivermectin.

Some authors of a widely reported meta-analysis of ivermectin studies that was flagged for including potentially fraudulent research have just posted a re-analysis on a preprint server — and ivermectin’s seemingly beneficial effects disappeared as trial quality went up.

For the re-analysis, Andrew Hill, PhD, of the University of Liverpool in England, and colleagues included 12 studies with 2,628 participants, and assessed them for bias. Overall, four studies had a low risk for bias, four studies had moderate risk, three studies were at high risk for bias, and one was potentially fraudulent.

Taken at face value, the overall meta-analysis found a 51% increase in survival with ivermectin (P=0.01), but excluding the potentially fraudulent trial, ivermectin’s benefit fell to 38% and was of borderline significance (P=0.05), they reported.

Taking out the studies with a high risk of bias led to a further drop — down to a nonsignificant 10% increase in survival (P=0.66), they noted. Further removing studies with a moderate risk of bias took the benefit down to 4% (P=0.9).

“This has made me more wary about trusting results when you don’t have access to the raw data,” Hill told MedPage Today in an interview. “We took them on trust and that was a mistake.”

Hill and his co-authors on the re-analysis — one who worked on the initial meta-analysis, and one who did not — published their findings on Research Square, the preprint server that also published the study that was ultimately found to be fraudulent and was retracted, though it had carried much of the benefit seen in the initial meta-analysis.

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