# Analysis of P Values in the Abstract Compared With the Main Text of Randomized Controlled Trials and Clinical Trials of Mesenchymal Stromal Cells for the Treatment of Knee Osteoarthritis

## TL;DR

This study found that abstracts of clinical trials on mesenchymal stromal cells for knee osteoarthritis are more likely to report significant results than the full papers, suggesting potential bias.

## Contribution

The study reveals a novel finding of selective reporting bias in abstracts of MSC trials for knee OA, with significant P values being over three times more likely to appear in abstracts than in full texts.

## Key findings

- 79.3% of P values in abstracts were significant, compared to 53.8% in main texts.
- The odds of significant P values being reported in abstracts were 3.3 times higher than in main texts.

## Abstract

Randomized controlled trials (RCTs) and clinical trials (CTs) are critical for evaluating treatment effectiveness, with abstracts serving as the primary source of the study that is read.

This study explored selective reporting of significant P values in the abstracts of RCTs and CTs on mesenchymal stromal cells (MSCs) for the treatment of knee osteoarthritis (OA). The purpose was to compare the rates of significant P values reported in the abstract compared with the main text of RCTs and CTs on MSCs for the treatment of knee OA.

Systematic review.

PubMed (MEDLINE) and Embase searches were conducted using related terms and were filtered for RCTs and CTs. There were 2 reviewers who analyzed the abstract and main text independently and extracted study characteristics and every P value reported in the abstract and main text of each article. The distribution of significant P values between the abstract and main text was compared using a paired-samples t test and odds ratios. Significance was set at P < .05.

The initial search yielded 156 articles, with 61 meeting the inclusion criteria. Our analysis showed a significant discrepancy in the distribution of P values between the abstract and main text. In abstracts, 79.3% of P values were significant compared with 53.8% in main texts. The odds of significant P values being reported in the abstract over the main text were more than 3 times higher (odds ratio, 3.3). The paired-samples t test confirmed that abstracts were significantly more likely to report significant findings (P = 7.5 × 10−8). Primary outcomes were reported in 90.2% of abstracts, with 18.0% being significant, 47.5% being not significant, and 34.4% being not applicable because of qualitative results. Functional and quality of life scores were the most common primary outcomes in 34 studies, followed by safety and adverse events in 25 studies, pain measurements in 20 studies, and imaging outcomes in 17 studies.

Our study highlights a significant risk of reporting bias in RCTs and CTs of MSCs for the treatment of knee OA. With growing interest in the use of MSCs, it remains crucial for busy clinicians to recognize the possibility of selective reporting bias in abstracts, as this could potentially influence clinical decision making.