Accuracy of time to treatment estimates in the CRASH-3 clinical trial: impact on the trial results

Digit preference and biased conclusions in cardiac arrest studies

BACKGROUND

In cardiac arrest (CA), time is directly predictive of patients' prognosis. The increase in mortality resulting from delayed cardiopulmonary resuscitation has been quantified minute by minute. Times reported in CA management studies could reflect a timestamping bias referred to as "digit preference". This phenomenon leads to a preference for certain numerical values (such as 2, 5, or 10) over others (such as 13). Our objective was to investigate whether or not digit preference phenomenon could be observed in reported times of the day related to CA management, as noted in a national registry.

METHODS

We analyzed data from the French National Electronic Registry of Cardiac Arrests. We analyzed twelve times-of-the-day corresponding to each of the main steps of CA management reported by the emergency physicians who managed the patients in prehospital settings. We postulated that if CA occurred at random times throughout the day, then we could expect to see events related to CA management occurring at a similar rate each minute of each hour of the day, at a fraction of 1/60. We compared the fraction of times reported as multiples of 15 (0, 15, 30, and 45 - on the hour, quarters, half hour) with the expected fraction of 4/60 (i.e. 4 × 1/60).

MAIN RESULTS

A total of 47,211 times-of-the-day in relation to 6131 CA were analyzed. The most overrepresented numbers were: 0, with 3737 occurrences (8% vs 2% expected, p < 0.0001) and 30, with 2807 occurrences (6% vs 2% expected, p < 0.0001). Times-of-the-day as multiples of 15 were overrepresented (22% vs 7% expected, p < 0.0001).

CONCLUSION

Prospectively collected times were considerably influenced by digit preference phenomenon. Studies that are not based on automatic time recordings and that have not evaluated and considered this bias should be interpretated with caution.

Effect of early tranexamic acid treatment on fatigue in patients with mild traumatic brain injury: data from the CRASH-3 clinical trial

Background: Each year world-wide about 65 million people sustain a mild traumatic brain injury (mTBI). Fatigue is a common and distressing symptom after mTBI. We examine the effect of tranexamic acid (TXA) on fatigue in patients with mTBI using data from the CRASH-3 trial. Methods: The CRASH-3 trial randomised 9,202 patients with traumatic brain injury and no significant extracranial bleeding to receive TXA or placebo within 3 hours of injury. The primary outcome was death from head injury within 28 days of injury. The methods and results are presented elsewhere. Fatigue was recorded as “None”, “Moderate” or “Extreme.” This study examines the effect of TXA on extreme fatigue in the 2,632 patients with mTBI (Glasgow Coma Scale [GCS] score≥13). Our analyses were not prespecified. Results: Our study primary outcome, extreme fatigue, was reported for 10 (0.8%) of 1,328 patients receiving TXA and 19 (1.5%) of 1,288 patients receiving placebo (risk ratio [RR]=0.51, 95% confidence interval [CI] 0.24-1.09). Death within 28 days of injury was reported for 34 (2.6%) of 1,328 patients receiving TXA versus 47 (3.6%) of 1,288 patients receiving placebo (RR=0.70, 95% CI 0.45-1.08). Among patients allocated to TXA, 44 (3.3%) patients either died or reported extreme fatigue versus 66 (5.1%) patients among those allocated to placebo (RR=0.65, 95% CI 0.44-0.94). Conclusions: Early tranexamic acid treatment may reduce fatigue in mTBI patients, but these results need to be confirmed in a larger trial. Registration: ISRCTN (ISRCTN15088122, 19/07/2011), ClinicalTrials.gov (NCT01402882, 26/07/2011), EudraCT (2011-003669-14, 25/07/2011), Pan African Clinical Trial Registry (PACTR20121000441277, 30/10/2012).