By Rebecca H. Allen, MD, MPH, Editor
Synopsis: In this randomized controlled trial, the use of transcutaneous electric nerve stimulation during endometrial biopsy did not clinically significantly reduce pain compared to placebo (median [interquartile range], 50 mm [20 mm to 80 mm] vs. 60 mm [40 mm to 100 mm]; P = 0.039), but was associated with increased satisfaction with the procedure.
Source: Wu J, Lim S, Scott A, et al. Transcutaneous electric nerve stimulation for analgesia during outpatient endometrial biopsy: A randomized controlled trial. Obstet Gynecol. 2025;145(1):e14-e23.
The office endometrial biopsy is a common procedure to evaluate abnormal uterine bleeding and postmenopausal bleeding. However, the best way to manage pain during the procedure is controversial.1 The authors of this study sought to evaluate transcutaneous electric nerve stimulation (TENS) as a means to reduce pain.
This was a double blind, randomized, placebo-controlled trial conducted at Duke University outpatient obstetrics and gynecology clinics between December 2022 and December 2023. Inclusion criteria were English- or Spanish-speaking adults who were scheduled for an endometrial biopsy. Exclusion criteria included use of TENS in the past, another procedure at the time of the endometrial biopsy, inability to follow instructions to use the TENS device, current use of any implanted electronic device (such as a pacemaker), and pregnancy.
Participants were randomized 1:1 to an active TENS unit or a placebo TENS unit. The four TENS pads were placed parallel to the spine at the T10-L1 and S2-S4 level. The patients could adjust the TENS setting themselves from 0 to 8 and were told to slowly adjust to the level when they felt a strong tingling sensation that is not painful. The electrodes were not connected to the device in the placebo arm.
Other pain interventions (e.g., nonsteroidal anti-inflammatory drugs [NSAIDs], heating pads, lidocaine) were allowed per provider/patient preference. The TENS unit turned on five minutes before the procedure and stopped five minutes after completion of the procedure. If the endometrial biopsy could not be completed, the participant was withdrawn from analysis.
The primary outcome measure was the pain score measured on the 100 mm Visual Analog Scale (VAS) immediately after the endometrial biopsy. Pain scores also were collected at speculum placement and at five minutes post-procedure and 15 minutes post-procedure. Other data collected included age, race, level of education, any history of endometrial biopsy, medication use, baseline pain and anxiety scores, satisfaction, anxiety with the procedure, and acceptability. The sample size was planned to be able to detect a 15 mm reduction on the 100 mm VAS in pain scores in the TENS group compared to the placebo group, which was thought to be a clinically significant difference in pain score.
The study enrolled and randomized 149 participants, 75 in the TENS group and 74 in the placebo group. After seven patients withdrew because of an inability to obtain the endometrial biopsy, there were 68 patients in the TENS group and 67 patients in the placebo group who were analyzed. The mean age was 50.9 years, 80% were parous, and 37% had undergone an endometrial biopsy in the past.
The two groups were similar in terms of baseline characteristics, including anxiety. A significant proportion of both groups used daily pain and anxiety medications (35.3% in the TENS group and 14.8% in the placebo group), which included acetaminophen, ibuprofen, and other NSAIDs; antidepressants; benzodiazepines; and opioids. At the time of the procedure, 10.3% of the TENS group and 6% of the placebo group used other interventions for pain, mostly warm compresses.
For the primary outcome, the TENS group had a lower pain score than the placebo group by 10 mm on the VAS (median [interquartile range], 50 mm [20 mm to 80 mm] vs. 60 mm [40 mm to 100 mm]; P = 0.039). There was no difference between the two groups for pain scores during speculum placement or post-procedure. There was greater satisfaction with pain control in the TENS group compared to the placebo group (median [interquartile range], 87.5 mm [60 mm to 100 mm] vs. 70 mm [41 mm to 100 mm]; P = 0.049).
Commentary
The office endometrial biopsy using the pipelle biopsy device typically is a rapid procedure but is associated with uterine cramping. Risk factors for pain can include nulliparity and postmenopausal status as well as pre-procedure anxiety. There is no agreed upon guideline on how to manage pain with this procedure.1
Some clinicians do not offer any analgesics. Nevertheless, NSAIDs often are recommended 30 to 60 minutes prior to the procedure. Another common intervention for pain is the intracervical or paracervical block. There also have been studies of intrauterine lidocaine instillation. Therefore, the authors of this study wanted to investigate the use of the TENS device.
TENS is a method of pain control that works by stimulating peripheral nerves with an electric current. The idea is that the electric current either blocks pain perception or changes one’s perception of the pain, or at least distracts a patient from the pain. The TENS device has minimal side effects and is available over the counter. TENS has been studied in several gynecologic procedures, including surgical abortion and hysteroscopy.2,3 A previous, smaller study had shown some benefit of TENS for endometrial biopsy pain 15 minutes after the procedure but not during the procedure.4 This study placed the pads on the abdomen, whereas most research showing efficacy for gynecologic procedures placed the pads on the back, where they are supposed to stimulate the uterine nerve roots. As such, the authors thought that repeating a randomized controlled trial with the pads on the back would be beneficial.
Overall, the study demonstrated a minimal decrease in pain using the TENS device: 10 mm on a 0 to 100 mm VAS. The authors did not think this decrease was clinically significant. Nevertheless, patients who received the device were somewhat more satisfied with the procedure and would recommend using it again. Often, patients are appreciative of any effort made to minimize their pain, even if it is not completely effective.
Although the study groups were balanced as part of a randomized trial, there were more subjects in the TENS group who used other interventions for pain, which may have influenced the results. In addition, it was difficult to blind the TENS group to the intervention. These limitations were acknowledged by the authors.
In conclusion, TENS is an option for an adjunctive pain control measure for the office endometrial biopsy. Whether this modality fits into clinic flow will depend on each office setting’s resources and staffing.
Rebecca H. Allen, MD, MPH, is Professor, Department of Obstetrics and Gynecology, Warren Alpert Medical School of Brown University, Women & Infants Hospital, Providence, RI.
References
1. Abbas AM, Samy A, El-Naser Abd El-Gaber Ali A, et al. Medications for pain relief in outpatient endometrial sampling or biopsy: A systematic review and network meta-analysis. Fertil Steril. 2019;112(1):140-148.e12.
2. Lisón JF, Amer-Cuenca JJ, Piquer-Mart S, et al. Transcutaneous nerve stimulation for pain relief during office hysteroscopy: A randomized controlled trial. Obstet Gynecol. 2017;129(2):363-370.
3. Lerma K, Goldthwaite LM, Blumenthal PD, Shaw KA. Transcutaneous electrical nerve stimulation for pain management of aspiration abortion up to 83 days of gestation: A randomized controlled trial. Obstet Gynecol. 2021;138(3):417-425.
4. Yilmazer M, Kose S, Arioz DT, et al. Efficacy of transcutaneous electrical nerve stimulation for pain relief in women undergoing office endometrial biopsy. Arch Gynecol Obstet. 2012;285(4):1059-1064.
In this randomized controlled trial, the use of transcutaneous electric nerve stimulation during endometrial biopsy did not clinically significantly reduce pain compared to placebo (median [interquartile range], 50 mm [20 mm to 80 mm] vs. 60 mm [40 mm to 100 mm]; P = 0.039), but was associated with increased satisfaction with the procedure.
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