Systematic reviews do not (yet) represent the ‘gold standard’ of evidence: A position paper

Background and Objective: This systematic review evaluated the effectiveness, tolerability and safety of cannabis-based medicines (CbMs) for chronic noncancer pain (CNCP) in long-term observational studies.Databases and Data Treatment: CENTRAL, EMBASE and MEDLINE were searched until December 2021. We included prospective observational studies with a study duration ≥26 weeks. Pooled estimates of event rates of categorical data and standardized mean differences (SMD) of continuous variables were calculated using a random effects model. Results:Six studies were included with 2686 participants, with study duration ranging between 26 and 52 weeks. Pain conditions included nociceptive, nociplastic, neuropathic and mixed pain mechanisms. The certainty of evidence for every outcome was very low. The weighted mean difference of mean pain reduction was 1.75 (95% confidence interval [CI] 0.72 to 2.78) on a 0-10 scale. 20.8% (95% CI 10.2% to 34.0%) of patients reported pain relief of 50% or greater. The effect size for sleep problems was moderate and for depression and anxiety was low. Study completions was reported for 53.3% (95% CI 26.8% to 79.9%) of patients, with dropouts of 6.8% (95% CI 4.3% to 9.7%) due to adverse events. Serious adverse events occurred in 3.0% (95 CI 0.02% to 12.8%) and 0.3% (95% CI 0.1% to 0.6%) of patients died. Conclusions:Information included in observational studies should be regarded with caution. Within the context of observational studies. CbMs had positive effects on multiple symptoms for some CNCP patients and were generally well tolerated and safe.Significance: There is very low quality evidence for the long-term effectiveness (pain, sleep, mood, health-related quality of life), tolerability and safety of medical cannabis for chronic non-cancer pain (CNCP) according to reports of prospective observational studies. Predefined criteria of a large magnitude of effect size in these types of studies were not met. Nevertheless, long-term medical cannabis therapy can be considered in some carefully selected and monitored patients with CNCP.

Section: Potential Biases In the Review (Limitations And Strengths)mentioning

confidence: 99%

Long‐term observational studies with cannabis‐based medicines for chronic non‐cancer pain: A systematic review and meta‐analysis of effectiveness and safety

Bialas

Fitzcharles

Klose

et al. 2022

“…Apart from the cohort of Bean et al, the included studies suffered from several biases, and their quality was globally poor. As recently stated., the small number of participants in several studies significantly decreases the confidence in their results (Moore et al, 2022). Furthermore, the results from cross‐sectional studies (Bean et al, 2016b; Dumas et al, 2011) should be read with caution.…”

Section: Discussionmentioning

confidence: 99%

Biological and psychological early prognostic factors in complex regional pain syndrome: A systematic review

Louis

Meyer

Legrain

et al. 2022

Background and objective Several risk factors for the onset of CRPS have been found, but evidence for prognostic factors associated with the progression of this condition remains sparse. However, the detection and management of these factors are necessary to design secondary prevention strategies. The objective of this systematic review was to identify prognostic factors in adult individuals with early CRPS. Database and data treatment PubMed, Embase, PsycINFO, Cochrane Library and Scopus, were published between January 1990 and November 2021. Two independent investigators selected cross‐sectional and longitudinal studies looking at early (<12 weeks from onset) prognostic factors for pain, CRPS severity score, disability, return to work, or quality of life. The quality in prognostic studies (QUIPS) tool was used to assess the risk of bias. A qualitative meta‐synthesis was performed. Results Out of 4652 different articles, six studies met the inclusion criteria. We identified 21 early factors associated with a poorer prognosis in type I CRPS. We found moderate evidence to support six of them: higher pain intensity, self‐rated disability, anxiety, pain‐related fear, being a female and high‐energy triggering event. Only two studies had an overall low risk of bias. Conclusions This study showed an important lack of information on early prognostic factors in CRPS. Only one article investigated the link with psychological characteristics. There is a crucial need for larger studies, with a well‐defined population using validated measures. Significance This systematic review highlights the lack of knowledge about early prognostic factors in CRPS. A few putative prognostic factors were identified. Most of the moderate evidence is related to a single cohort. Future research is required to find out which patients are vulnerable to chronification.

“…The other meta‐analysis showed that MT reduces pain with a larger effect size ( I 2 = 82%; standardized mean difference = −0.81; 95% CI = −1.36 to −0.25; p = 0.005) compared with other methods (Wang et al, 2021 ). However, the conclusion of these meta‐analyses are subject of debate due to questionable methodological and statistical choices: the use of fixed‐effect analyses (Borenstein et al, 2010 ), the inclusion of low‐powered and poor‐quality studies, the strong heterogeneity and the interpretation of non‐clinically relevant effects (Moore et al, 2022 ). Furthermore, no systematic review has evaluated MT impact on the patients' quality of life and disability.…”

Section: Introductionmentioning

confidence: 99%

Effect of mirror therapy in the treatment of phantom limb pain in amputees: A systematic review of randomized placebo‐controlled trials does not find any evidence of efficacy

Guémann¹,

Olié

Raquin³

et al. 2022

Background and Objective: Phantom limb pain (PLP) concerns >50% of amputees and has a negative impact on their rehabilitation, mental health, and quality of life. Mirror therapy (MT) is a promising strategy, but its effectiveness remains controversial. We performed a systematic review to: (i) evaluate the effectiveness of MT versus placebo in reducing PLP, and (ii) determine MT effect on disability and quality of life.Databases and Data Treatment: We selected randomized controlled trials in five databases (Medline, Cochrane Library, CINAHL, PEDro, and Embase) that included patients with unilateral lower or upper limb amputation and PLP and that compared the effects on PLP of MT versus a placebo technique. The primary outcome was PLP intensity changes and the secondary outcomes were PLP duration, frequency, patients' disability and quality of life.Results: Among the five studies included, only one reported a significant difference between the MT group and control group, with a positive MT effect at week 4. Only one study assessed MT effect on disability, and found a significant improvement in the MT group at week 10 and month 6. Conclusions: Our systematic review did not allow concluding that MT reduces PLP and disability in amputees. This lack of strong evidence is probably due to (i) the low methodological quality of the included studies, and (ii) the lack of statistical power. Future trials should include a higher number of patients, increase the number and frequency of MT sessions, have a long-term follow-up, and improve the methodological quality. SIGNIFICANCERecent meta-analyses concluded that mirror therapy is effective for reducing phantom limb pain. Conversely, the present systematic review that included only studies with the best level of evidence did not find any evidence about its effectiveness for this condition. We identified many ways to improve future randomized controlled trials on this topic: increasing the number of participants, reducing the intra-group heterogeneity, using a suitable placebo, and intensifying the mirror therapy sessions and frequency.