Probability of adverse events that have not yet occurred: a statistical reminder

Eypasch, E.; Lefering, Rolf; Kum, C. K.; Troidl, H.

doi:10.1136/bmj.311.7005.619

Cited by 296 publications

(193 citation statements)

References 12 publications

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“…This simple rule to quickly calculate the upper limit of a 95 % confidence interval states that if a certain event did not occur in a sample of n subjects, the upper limit of the 95 % confidence interval surrounding this data is equal to 3/n. When n is greater than 30, this is a good approximation of the upper limit of the 95 % confidence interval [4]. For example, in these data on iocane powder, the approximate upper limit of risk of a major outcome with 95 % certainty is 3/32=9.4 %, very close to the calculated number above.…”

supporting

confidence: 52%

The Poison Pen: How Confident Are We About Iocane?

Stellpflug

Cole

2014

J. Med. Toxicol.

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We report a retrospective case series of exposures to iocane powder, a deadly, odorless, tasteless, and absolutely fictional poison [1]. A 10-year review of an imaginary Sicilian Poison Center database revealed 32 exposures, coincidentally all ingestions from wine goblets. There were 29 (90.6 %) patients with no clinical effects, 2 (6.3 %) with minor effects, 1 (3.1 %) with a moderate effect and 0 with major effects. No deaths occurred and no patient suffered permanent sequelae. These data show that iocane exposure is not universally fatal, as previously thought. Given the apparent relative safety, with less than 10 % of patients experiencing clinical effects, poison centers may choose to allow asymptomatic exposed patients to be observed at home. Is the conclusion valid, and more importantly, safe? This sort of abstract is common to our academic experience in medical toxicology, including those featured in JMT associated with the ACMT Annual Scientific Meeting. We survey retrospective or prospective experience and attempt to draw conclusions to guide our future management. Often times, this sort of research produces our best available data because of our inability to safely (or ethically) poison people in a blinded and random fashion. That being true, authors of this type of abstract need to take caution in projecting future management unless they are also willing to inform the reader how confident they are in their recommendations. Authors cannot be expected, at least in brief abstract form, to explain the multiple confounding biases of their study population. However, they should be held responsible to let the reader know how likely the same result would be if someone repeated the same study on a representative patient population at their own institution. This would give the reader an immediate idea of how they should use the presented information to affect their own practice. It would likely, in many cases, even force the authors to soften existing conclusions or change them entirely. If only there was an easy way to portray the confidence in the presented data.Simple application of confidence intervals surrounding the proportions presented in the above abstract rounds out the presented information appropriately; this forces a more accurate and softened conclusion. This can obviously be accomplished with the help of a statistician who can then also help account for biases and other potential fallacies. In crude fashion, it can be done just through the use of an online confidence interval calculator, reachable with a search of "confidence interval calculator" or "Clopper-Pearson calculator"; results will vary slightly depending on which mode of calculation the online calculator uses [2].Note the addition of confidence interval (CI) below, the appropriately altered conclusion, and how potentially inaccurate and worrisome the above recommendations were:We report a retrospective case series of exposures to iocane powder, a reportedly deadly, odorless, tasteless, and absolutely fictional poison [1]. A 10-year rev...

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supporting

confidence: 52%

The Poison Pen: How Confident Are We About Iocane?

Stellpflug

Cole

2014

J. Med. Toxicol.

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“…10 With 89 subjects randomized to the patch, we can conclude with 95% confidence that the true adverse event rate is <3.3% for the study group. We did not expect the unintentional randomization of more premature infants to the study group.…”

Section: Patients and Cathetersmentioning

confidence: 99%

A silver–alginate-coated dressing to reduce peripherally inserted central catheter (PICC) infections in NICU patients: a pilot randomized controlled trial

Baldwin

Slaughter

et al. 2009

J Perinatol

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Objective: Our aim was to evaluate the safety of a silver-alginatecontaining dressing to reduce peripherally inserted central catheter (PICC) infections in neonatal intensive care unit (NICU) patients.Study Design: Patients were randomized 3:1 to receive a patch containing silver, alginate and maltodextrin or standard of care. Patches were placed under the regular transparent retention dressing at the PICC exit site at insertion and were replaced with every dressing change at least every 2 weeks until PICC discontinuation. All study infants were monitored for adverse skin reactions.Result: A total of 100 infants were followed up for 1922 person-days, including 75 subjects with 89 PICCs who received the patch. The median birth weight (1330 g) and median gestational age (30 weeks) was lower in the patch group when compared with the controls (P ¼ 0.001 and 0.005, respectively). Study patients received the patch with their PICC at a median age of 5 days; the patch stayed in place for a median of 13 days. We noted no adverse skin reactions and found no evidence that the patch alters the microbiology of PICC-associated infections.Conclusion: This pilot trial suggests that silver-alginate-coated dressings are skin safe and their inclusion in future trials aimed at reduction of PICC-associated bloodstream infections in the NICU should be considered.

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“…If no repeated reporting of same cases has taken place within this population, only 1 case with a life threatening situation has occurred, with no mortality or permanent disability. A simple calculation of the upper limit of 95% confidence interval (3/n) for occurrence of accident resulting in death or handicap gives 1/1000 with the current experience (Eypasch et al 1995). It must be noted, however, that a major proportion of the cases have been reported in abstracts based on audit or regional database data which may not include all the necessary data for exclusion of near miss situations or even major accidents.…”

Section: Sedation and Dizzinessmentioning

confidence: 99%

Intravenous patient-controlled analgesia with remifentanil in early labour

Volmanen¹

2011

Acta Anaesthesiologica Scandinavica

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Cover design Raimo Ahonen JUVENES PRINT TAMPERE 2010Volmanen, Petri, Intravenous patient controlled analgesia with remifentanil in early labour. AbstractIn four prospective clinical trials, 114 parturients used intravenous patient-controlled remifentanil analgesia during the 1 st stage of labour. The median effective dose per bolus was ascertained to be 0.4 μg/kg and the pain scores were reduced with this by a median of 2 on a numerical scale (0-10). Compared with nitrous oxide, 15 parturients included in a cross-over study reported a larger reduction in pain scores during remifentanil analgesia (1.5 vs. 0.5, p = 0.001) and better pain relief scores (2.5 vs. 0.5 on a ranked five point scale 0-4, p < 0.001). In a parallel study including 45 parturients, epidural analgesia (EDA, 20 ml bupivacaine 0.625 mg/ml and fentanyl 2 μg/ml) was associated with lower pain scores (5.2 vs. 7.3 with remifentanil, p = 0.004) but variables related to satisfaction with analgesia (pain relief score, proportion of mothers with desire to continue with the given medication and termination of the study due to inadequate pain relief) were similar. A comparison of two methods for timing the remifentanil bolus during the uterine contraction cycle suggested that delaying the bolus does not improve analgesia. A period effect was noted in the cross-over trial with higher pain scores and increased drug consumption during the second study period suggesting acute hyperalgesia.Side effects of remifentanil analgesia included respiratory depression warranting oxygen supplementation in 33% of parturients. Sedation was experienced by the parturients using remifentanil and this was scored as stronger than sedation during nitrous oxide and EDA. The number of parturients with nausea did not increase during remifentanil analgesia. Other maternal side effects included dizziness, a difficulty in visual focusing and itching. Foetal heart rate tracing abnormalities were noted. The incidence of abnormal tracings and decreased UapH were not different, however, from that observed during nitrous oxide or EDA. Apgar scores at 1 and 5 minute indicated no neonatal depression. Keywords

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Probability of adverse events that have not yet occurred: a statistical reminder

Cited by 296 publications

References 12 publications

The Poison Pen: How Confident Are We About Iocane?

The Poison Pen: How Confident Are We About Iocane?

A silver–alginate-coated dressing to reduce peripherally inserted central catheter (PICC) infections in NICU patients: a pilot randomized controlled trial

Intravenous patient-controlled analgesia with remifentanil in early labour

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