Publication bias affected the estimate of postoperative nausea in an acupoint stimulation systematic review

Impact evaluation of CONSORT and STRICTA guidelines on reporting quality for randomized controlled trials of acupuncture conducted in China

OBJECTIVE

To evaluate and compare the reports' qualities of acupuncture randomized controlled trials (RCTs) conducted in China before and after the implementation of two guidelines, i.e., the Consolidated Standards of Reporting Trials (CONSORT) statement and the Standards for Reporting Interventions in Controlled Trials of Acupuncture (STRICTA).

METHODS

Proportions of studies that reported CONSORT and STRICTA items were compared for the years before and after implementation of these two guidelines. In addition, the total score of each item's reporting were calculated and reported differences during different date ranges were compared.

RESULTS

For CONSORT items (maximum score 8), there was evidence of a slight improvement in reporting between 1994-1995 and 1999-2000 combined (2.5±0.6) and 2004-2005 and 2009-2010 combined (3.0±0.9; difference 0.4, 95% confidence interval, 0.3 to 0.6, P<0.01). For STRICTA items (maximum score 17), there was evidence that a slight improvement in reporting between 1994-1995 and 1999-2000 combined (8.6±2.1) and 2004-2005 and 2009-2010 combined (10.1±1.8; difference 1.5, 95% confidence interval, 1.1 to 1.9, P<0.01).

CONCLUSION

Quality of reporting for RCTs of acupuncture treatment conducted in China have generally improved since the introduction of the STRICTA and CONSORT guidelines.

Stimulation of the wrist acupuncture point PC6 for preventing postoperative nausea and vomiting

BACKGROUND

Postoperative nausea and vomiting (PONV) are common complications following surgery and anaesthesia. Antiemetic drugs are only partially effective in preventing PONV. An alternative approach is to stimulate the PC6 acupoint on the wrist. This is an update of a Cochrane review first published in 2004, updated in 2009 and now in 2015.

OBJECTIVES

To determine the effectiveness and safety of PC6 acupoint stimulation with or without antiemetic drug versus sham or antiemetic drug for the prevention of PONV in people undergoing surgery.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (Cochrane Library, Issue 12, 2014), MEDLINE (January 2008 to December 2014), EMBASE (January 2008 to December 2014), ISI Web of Science (January 2008 to December 2014), World Health Organization Clinical Trials Registry, ClinicalTrials.gov, and reference lists of articles to identify additional studies. We applied no language restrictions.

SELECTION CRITERIA

All randomized trials of techniques that stimulated the PC6 acupoint compared with sham treatment or drug therapy, or combined PC6 acupoint and drug therapy compared to drug therapy, for the prevention of PONV. Interventions used in these trials included acupuncture, electro-acupuncture, transcutaneous electrical acupoint stimulation, transcutaneous nerve stimulation, laser stimulation, capsicum plaster, acu-stimulation device, and acupressure in people undergoing surgery. Primary outcomes were the incidences of nausea and vomiting after surgery. Secondary outcomes were the need for rescue antiemetic therapy and adverse effects.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted the data and assessed the risk of bias domains for each trial. We used a random-effects model and reported risk ratio (RR) with associated 95% confidence interval (95% CI). We used trial sequential analyses to help provide information on when we had reached firm evidence in cumulative meta-analyses of the primary outcomes, based on a 30% risk ratio reduction in PONV.

MAIN RESULTS

We included 59 trials involving 7667 participants. We rated two trials at low risk of bias in all domains (selection, attrition, reporting, blinding and other). We rated 25 trials at high risk in one or more risk-of-bias domains. Compared with sham treatment, PC6 acupoint stimulation significantly reduced the incidence of nausea (RR 0.68, 95% CI 0.60 to 0.77; 40 trials, 4742 participants), vomiting (RR 0.60, 95% CI 0.51 to 0.71; 45 trials, 5147 participants) and the need for rescue antiemetics (RR 0.64, 95% CI 0.55 to 0.73; 39 trials, 4622 participants). As heterogeneity among trials was substantial and there were study limitations, we rated the quality of evidence as low. Using trial sequential analysis, the required information size and boundary for benefit were reached for both primary outcomes.PC6 acupoint stimulation was compared with six different types of antiemetic drugs (metoclopramide, cyclizine, prochlorperazine, droperidol. ondansetron and dexamethasone). There was no difference between PC6 acupoint stimulation and antiemetic drugs in the incidence of nausea (RR 0.91, 95% CI 0.75 to 1.10; 14 trials, 1332 participants), vomiting (RR 0.93, 95% CI 0.74 to 1.17; 19 trials, 1708 participants), or the need for rescue antiemetics (RR 0.87, 95% CI 0.65 to 1.16; 9 trials, 895 participants). We rated the quality of evidence as moderate, due to the study limitations. Using trial sequential analyses, the futility boundary was crossed before the required information size was surpassed for both primary outcomes.Compared to antiemetic drugs, the combination of PC6 acupoint stimulation and antiemetic therapy reduced the incidence of vomiting (RR 0.56, 95% CI 0.35 to 0.91; 9 trials, 687 participants) but not nausea (RR 0.79, 95% CI 0.55 to 1.13; 8 trials, 642 participants). We rated the quality of evidence as very low, due to substantial heterogeneity among trials, study limitations and imprecision. Using trial sequential analysis, none of the boundaries for benefit, harm or futility were crossed for PONV. The need for rescue antiemetic was lower in the combination PC6 acupoint stimulation and antiemetic group than the antiemetic group (RR 0.61, 95% CI 0.44 to 0.86; 5 trials, 419 participants).The side effects associated with PC6 acupoint stimulation were minor, transient and self-limiting (e.g. skin irritation, blistering, redness and pain) in 14 trials. Publication bias was not apparent in the contour-enhanced funnel plots.

AUTHORS' CONCLUSIONS

There is low-quality evidence supporting the use of PC6 acupoint stimulation over sham. Compared to the last update in 2009, no further sham comparison trials are needed. We found that there is moderate-quality evidence showing no difference between PC6 acupoint stimulation and antiemetic drugs to prevent PONV. Further PC6 acupoint stimulation versus antiemetic trials are futile in showing a significant difference, which is a new finding in this update. There is inconclusive evidence supporting the use of a combined strategy of PC6 acupoint stimulation and antiemetic drug over drug prophylaxis, and further high-quality trials are needed.

Acupressure at acupoint P6 for prevention of postoperative nausea and vomiting: a randomised clinical trial

BACKGROUND AND OBJECTIVE

Postoperative nausea and vomiting causes discomfort in many patients despite both antiemetic prophylactics and improved anaesthetic techniques. Stimulation of acupoint P6 is described as an alternative method for prophylaxis of postoperative nausea and vomiting.In a randomised, double-blinded study, we aimed to investigate the effect of P6 acupoint stimulation on the incidence of postoperative nausea and vomiting within 24 h postoperatively with an acupressure wristband: Vital-Band.

METHODS

One hundred and thirty-four healthy, non-smoking women scheduled for breast surgery were randomised either to P6 stimulation or to sham control. Wristbands were applied and covered with a dressing before induction of anaesthesia. Follow-up was carried out three times within 24 h postoperatively. Primary outcomes were postoperative nausea and/or vomiting.

RESULTS

One hundred and twelve patients completed the study. There were no statistically significant differences in the incidence of nausea [P6 stimulation, 35.1% (95% confidence interval, CI 22.7-47.5%) versus sham control, 43.1% (95% CI 29.5-56.7%; P = 0.433)] or vomiting [P6 stimulation, 25.9% (95% CI 14.6-37.2%) versus sham control, 26.9% (95% CI 14.8-39.0%; P = 1.000)]. Approximately, one third of the patients reported side effects caused by the wristband, for example, redness, swelling and tenderness.

CONCLUSION

We did not find the Vital-Band effective in preventing either nausea or vomiting after operation in women undergoing breast surgery.

Confidence intervals for random effects meta-analysis and robustness to publication bias

The DerSimonian-Laird confidence interval for the average treatment effect in meta-analysis is widely used in practice when there is heterogeneity between studies. However, it is well known that its coverage probability (the probability that the interval actually includes the true value) can be substantially below the target level of 95 per cent. It can also be very sensitive to publication bias. In this paper, we propose a new confidence interval that has better coverage than the DerSimonian-Laird method, and that is less sensitive to publication bias. The key idea is to note that fixed effects estimates are less sensitive to such biases than random effects estimates, since they put relatively more weight on the larger studies and relatively less weight on the smaller studies. Whereas the DerSimonian-Laird interval is centred on a random effects estimate, we centre our confidence interval on a fixed effects estimate, but allow for heterogeneity by including an assessment of the extra uncertainty induced by the random effects setting. Properties of the resulting confidence interval are studied by simulation and compared with other random effects confidence intervals that have been proposed in the literature. An example is briefly discussed.

Stimulation of the wrist acupuncture point P6 for preventing postoperative nausea and vomiting

BACKGROUND

Postoperative nausea and vomiting (PONV) are common complications following surgery and anaesthesia. Drugs to prevent PONV are only partially effective. An alternative approach is to stimulate the P6 acupoint on the wrist. This is an update of a Cochrane review first published in 2004.

OBJECTIVES

To determine the efficacy and safety of P6 acupoint stimulation in preventing PONV.

SEARCH STRATEGY

We searched CENTRAL (The Cochrane Library, Issue 3, 2008), MEDLINE (January 1966 to September 2008), EMBASE (January 1988 to September 2008), ISI Web of Science (January 1965 to September 2008), the National Library of Medicine publication list of acupuncture studies, and reference lists of articles.

SELECTION CRITERIA

All randomized trials of techniques that stimulated the P6 acupoint compared with sham treatment or drug therapy for the prevention of PONV. Interventions used in these trials included acupuncture, electro-acupuncture, transcutaneous nerve stimulation, laser stimulation, capsicum plaster, an acu-stimulation device, and acupressure in patients undergoing surgery. Primary outcomes were the risks of nausea and vomiting. Secondary outcomes were the need for rescue antiemetic therapy and adverse effects.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and extracted the data. We collected adverse effect information from the trials. We used a random-effects model and reported relative risk (RR) with associated 95% confidence intervals (95% CI).

MAIN RESULTS

We included 40 trials involving 4858 participants; four trials reported adequate allocation concealment. Twelve trials did not report all outcomes. Compared with sham treatment P6 acupoint stimulation significantly reduced: nausea (RR 0.71, 95% CI 0.61 to 0.83); vomiting (RR 0.70, 95% CI 0.59 to 0.83), and the need for rescue antiemetics (RR 0.69, 95% CI 0.57 to 0.83). Heterogeneity among trials was moderate. There was no clear difference in the effectiveness of P6 acupoint stimulation for adults and children; or for invasive and noninvasive acupoint stimulation. There was no evidence of difference between P6 acupoint stimulation and antiemetic drugs in the risk of nausea (RR 0.82, 95% CI 0.60 to 1.13), vomiting (RR 1.01, 95% CI 0.77 to 1.31), or the need for rescue antiemetics (RR 0.82, 95% CI 0.59 to 1.13). The side effects associated with P6 acupoint stimulation were minor. There was no evidence of publication bias from contour-enhanced funnel plots.

AUTHORS' CONCLUSIONS

P6 acupoint stimulation prevented PONV. There was no reliable evidence for differences in risks of postoperative nausea or vomiting after P6 acupoint stimulation compared to antiemetic drugs.