Evidence
This page contains a snapshot of featured content which highlights evidence addressing key clinical questions including areas of uncertainty. Please see the main topic reference list for details of all sources underpinning this topic.
BMJ Best Practice evidence tables
Evidence tables provide easily navigated layers of evidence in the context of specific clinical questions, using GRADE and a BMJ Best Practice Effectiveness rating. Follow the links at the bottom of the table, which go to the related evidence score in the main topic text, providing additional context for the clinical question. Find out more about our evidence tables.
This table is a summary of the analysis reported in a guideline (underpinned by a systematic review) that focuses on the above important clinical question.
Confidence in the evidence is very low or low where GRADE has been performed and the intervention may be more effective/beneficial than the comparison for key outcomes. However, this is uncertain and new evidence could change this in the future.
Population: Patients with suspected anaphylaxis
Intervention: One (earlier) timing of mast cell tryptase testing ᵃ
Comparison: Any other (later) timing ᵃ
| Outcome | Effectiveness (BMJ rating)? | Confidence in evidence (GRADE)? |
|---|---|---|
Timing of peak mast cell tryptase | See note ᵇ | Very Low |
End-point of elevated mast cell tryptase | See note ᶜ | Very Low |
Recommendations as stated in the source guideline After a suspected anaphylactic reaction in adults or young people aged 16 years or older, take timed blood samples for mast cell tryptase testing as follows: A sample as soon as possible after emergency treatment has started A second sample ideally within 1-2 hours (but no later than 4 hours) from the onset of symptoms.
Note The guideline committee stated that the timing of the first blood sample should be as soon as possible since the evidence suggests a median time of 30 minutes for the peak of mast cell tryptase, and that the peak was reached within two hours in all but two patients. ᵃ The guideline committee did not identify any randomised controlled trials (RCTs) so they included observational studies. ᵇ The guideline committee noted that the timing of peak levels ranged from 1 minute to 6 hours (median 30 minutes, 7 studies, N=178) and that levels were reported as median 24 units per litre (range 4.09–66.2). ᶜ The guideline committee also noted the half-life of tryptase ranged from 30 minutes to 300 minutes (median 90 minutes, 6 studies, N=147) with levels returning to normal by 24 hours after onset of symptoms. Normal levels were reported at six hours in one study.
This evidence table is related to the following section/s:
This table is a summary of the analysis reported in a systematic review that focuses on the above important clinical question.
Confidence in the evidence is high or moderate to high where GRADE has been performed and there is no difference in effectiveness between the intervention and comparison for key outcomes.
Population: Critically ill adults in intensive care units or high dependency units
Intervention: Balanced crystalloid solution
Comparison: Normal saline
| Outcome | Effectiveness (BMJ rating)? | Confidence in evidence (GRADE)? |
|---|---|---|
All-cause mortality at 90 days ᵃ | No statistically significant difference ᵇ | High |
Incidence of acute kidney injury | No statistically significant difference | Moderate |
New treatment with renal replacement therapy | No statistically significant difference | Low |
Ventilator-free days (to day 28) | No statistically significant difference | Moderate |
Vasopressor-free days (to day 28) | No statistically significant difference | High |
Health-related quality of life | See note ᶜ | GRADE assessment not performed for this outcome |
Note The reviewers noted that the limitations of this review are mostly related to the characteristics of the included trials, which reported outcomes at different time points and used different definitions for outcome measures such as acute kidney injury. Furthermore, many of the studies did not include or did not report outcomes in subgroups of interest, resulting in limited power to detect clinically important subgroup effects. None of the included studies reported on longer-term quality of life or functional outcomes. ᵃ Primary outcome as stated in the systematic review underpinning this evidence table. ᵇ The estimated effect of balanced crystalloids versus normal saline ranges from a 9% relative reduction to a 1% relative increase in the risk of death; high probability that the average effect of using balanced crystalloids was to reduce mortality; RR 0.96 (95% CI 0.91 to 1.01). The reviewers noted that this estimate of effect was stable when including low risk-of-bias studies only or when including all studies regardless of risk-of-bias. The authors of the systematic review also noted that reduction in mortality was significant if a Bayesian approach was taken. ᶜ No data was available to provide a pooled estimate of quality of life.
This evidence table is related to the following section/s:
Cochrane Clinical Answers
Cochrane Clinical Answers (CCAs) provide a readable, digestible, clinically focused entry point to rigorous research from Cochrane systematic reviews. They are designed to be actionable and to inform decision making at the point of care and have been added to relevant sections of the main Best Practice text.
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