Departments of Gynaecology and Medical Statistics, Leiden University Medical Center, P.O.Box 9600, 2300 RC Leiden, The Netherlands
1 To whom correspondence should be addressed. e-mail: f.w.jansen{at}lumc.nl
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Abstract |
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Key words: contraception/follow-up/gynaecological examination/intrauterine device/transvaginal ultrasound
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Introduction |
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Currently, transvaginal ultrasound (TVU) is used increasingly to complete the gynaecological examination in hospital settings (Valentin, 1999). The routine use of TVU to monitor the position of the IUD after insertion has been advocated (Bonilla-Musoles et al., 1996
). There is much evidence that shows TVU to be highly accurate in monitoring the location of any type of IUD (Petta et al., 1996
; Faúndes et al., 1997
, 2000; Palo, 1997
; Aleem et al., 1992
). The IUDendometrium distance (IUDED) seems to be the most relevant measurement, especially for copper IUD (Petta et al., 1996
; Faúndes et al., 1997
, 2000). However, the maximum IUDED to ensure adequate contraception is under debate (Petta et al., 1996
; Faúndes et al., 1997
), especially since T-shaped IUD tend to accommodate in their position during the first 3 months after insertion (Faúndes et al., 2000
). Therefore removal of all abnormally located IUD at TVU may result in a high number of unnecessary removals (Petta et al., 1996
; Faúndes et al., 2000
).
The silent incorporation of routine TVU in gynaecology and especially in IUD follow-up needs urgent evaluation (Valentin, 1999; Rivera and Best, 2002
). Before adopting the routine use of TVU for this purpose, and consequently transfer the insertion of IUD from general practice to the gynaecological outpatient department, the clinical value of this phenomenon should be evaluated and guidelines adjusted accordingly. The aim of this prospective study was to evaluate the clinical relevance of the routine use of TVU immediately after and 6 weeks after the insertion of an IUD.
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Materials and methods |
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The clinician who inserted the IUD had to fill out a standardized form with questions about the procedure: (i) whether the IUD was thought to be located properly (adequate position) or erroneously (indadequate position) inside the uterine cavity; and (ii) whether the procedure was with or without complications and/or difficulties. Clinicians were divided into groups according to their experience (respectively <25, 2575 and >75 inserted IUD).
Immediately after the insertion of an IUD, an independent sonographer who was unaware of the clinicians answers to the above-mentioned questions performed TVU. A 57.5 MHz multifrequency vaginal probe and a Power Vision 6000 ultrasound machine (Toshiba Medical Systems, The Netherlands) were used. With TVU, the distance between the top of the vertical arm of the IUD and the junction between the endometrium and the uterine cavity (IUDED) was measured in the mid-longitudinal plane (Figure 1). Whenever this junction could not be identified clearly, the IUDED was calculated by subtracting half of the double endometrial thickness from the distance from the top of the IUD until the endo-myometrial junction (Figure 2) (Petta et al., 1996; Faúndes et al., 1997
; 2000). The mean IUDED was calculated from three independent measurements. In 20 non-selected consecutive women, a reliability analysis was performed by means of calculation of the intra-class correlation of two independent IUDED measurements (Khan and Chien, 2001
; Sackett and Haynes, 2002
).
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The predictive values and likelihood ratios with 95% confidence intervals (95% CI) of the clinical evaluation of IUD localization were calculated using the IUDED as the gold standard. A multiregression analysis was used to calculate the multivariate odds ratios (OR with 95% CI) of risk factors for inadequate insertion and inadequate IUD position at follow-up. Multivariate OR (with 95% CI) were also calculated for risk factors for improper clinical evaluation of the position of the IUD both immediately after insertion and at follow-up. Students t-test (continuous data), 2-test and Fishers exact test (categorical data) were used to compare groups; the level of significance was set at P < 0.05.
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Results |
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Validity analysis
After insertion, the clinician was certain about adequate position of the IUD in 175 cases (90%). According to the IUDED measurements, 172 of these IUD were positioned adequately [negative predictive value (NPV) of clinical evaluation: 0.98; 95% CI: 0.961.00]. According to the clinician, the IUD was positioned inadequately in 20 cases (10%), in 12 of these the IUDED was indeed >5.0 mm [positive predictive value (PPV) of clinical evaluation: 0.6; 95% CI: 0.390.81]. The 2x2 table and likelihood ratios (with 95% CI) are shown in Table I. In a total of 15 women, the IUDED was >5.0 mm. In eight of these women, the IUD was removed because of this erroneous location.
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Of the remaining 173 women, the clinician was certain about the adequate position of the IUD in 160 (91.9%) women. In all these women, the IUDED was 5.0 mm (NPV of the clinical evaluation at follow-up: 1.0). In 13 women (8.1%) the clinician concluded, according to the results of the gynaecological interview and pelvic examination, that the IUD was located inadequately. In six of these, the IUDED was indeed located >5.0 mm (PPV of the clinical evaluation at follow-up: 0.54; 95% CI: 0.260.81). In seven women, the IUD had been inserted inadequately; in two of these women, the IUD was still located inadequately at follow-up. In the remaining five women, the IUD had migrated upwards to an adequate intrauterine position. The 2x2 tables and likelihood ratios of the clinical evaluation of IUD position are shown in Table II.
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Multiregression analysis: correctness of clinical evaluation
Immediately after insertion, the clinician evaluated the position of the IUD to be incorrect in 11 cases (5.6%; eight false negative evaluations and three false positive evaluations). Complicated insertion was the only significant predictor of incorrect clinical evaluation (OR: 2.89; 95% CI: 1.256.67, P = 0.01). Inexperience (<25 inserted IUD) was not of significant influence in the incorrect clinical evaluation immediately after insertion (OR: 1.81; 95% CI: 0.369.2; P = 0.47). At follow-up, the clinical evaluation was incorrect in six cases (3.5%; all false negative evaluations). Complaints at follow-up was the only significant predictive variable (OR: 11.09; 95% CI: 1.5181.39, P = 0.02). Again, inexperience was not a significant variable for improper clinical evaluation (OR: 0.71; 95% CI: 0.114.7; P = 0.71). At follow-up, highly experienced clinicians did not significantly more often evaluate the position of the IUD incorrectly (OR: 1.39; 95% CI: 0.228.91, P = 0.69).
Reliability analysis
The intra-class correlation (alpha) for repeatability was 0.99 (95% CI: 0.980.99). Table III shows the reliability analysis of the IUDED measurement stratified for type of IUD.
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Discussion |
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In our opinion, the development of evidence-based guidelines for the insertion of an IUD and follow-up of IUD users is mandatory (Rivera and Best, 2002). Although the IUD is used infrequently, despite its reliability and cost-effectiveness (Mishell, 1998
), its use may increase because of three reasons. First, nulliparity is no longer a contraindication (Hubacher et al., 2001
). Second, the levonorgestrel-releasing intrauterine system has been shown to be highly effective for the treatment of menorrhagia and dysfunctional uterine bleeding (Crosignani et al., 1997
; Monteiro et al., 2002
). Third, due to recent attention to the increased risk of venous thrombosis as a result of the use of oral contraceptives, especially third generation combined oral contraceptives, some women may switch from hormonal to non-hormonal contraceptive methods (Vandenbroucke et al., 2001
).
As suggested for proper diagnostic research (Sackett and Haynes, 2002), we minimized the bias of the sonographer since he was unaware of both the opinion of the clinician about the position of the IUD and of the difficulties at insertion; the sonographer was also unaware of the conclusion of the clinical evaluation at follow-up. However, for ethical reasons it was not possible to withhold the results of the TVU immediately after insertion to the clinicians and the patients. This may have biased both the sonographer and the clinician in their evaluation at follow-up, especially in the seven women with inadequate position of the IUD after insertion.
Our results indicate that clinicians with relatively little experience in inserting and monitoring IUD, like most general practitioners, are still capable of doing so. The number of incorrect clinical evaluations of IUD position did not differ significantly between inexperienced (<25 IUD inserted) and experienced (>25 IUD inserted) clinicians, either immediately after insertion or at follow-up (OR respectively: 1.81; 95% CI: 0.399.2; and 0.71; 95% CI: 0.114.7). Inexperienced and experienced clinicians were equally accurate in inserting IUD (OR: 1.67; 95% CI: 0.319.2).
TVU has been shown to be able to monitor the position of all different types of IUD (Bonilla-Musoles et al., 1996; Petta et al., 1996
; Faúndes et al., 1997
, 2000; Palo 1997
); however, this is the first report on the excellent reliability of the IUDED measurement by TVU (intra-class coefficient 0.99). We choose 5.0 mm as threshold for abnormal IUD position as consensus between earlier reports. First Faúndes showed that in 90% of women without complaints of their copper IUD, the IUDED was <7.0 mm (Faúndes et al., 1997
). Petta showed that if IUD were removed whenever the IUDED was >3.0 mm, this resulted in a significant reduction in spontaneous expulsion (Petta et al., 1996
). Since there is no evidence concerning the optimal IUDED for levonorgestel-releasing intrauterine systems, we also decided to use 5.0 mm, although there are reasons to believe that this particular IUD might be as effective, both in the prevention of pregnancy as well as for the treatment of menorrhagia, if it is located more cervically (Andersson and Rybo, 1990
; Andersson et al., 1994
). Whether 5.0 mm is the most effective IUDED to ensure adequate contraception remains to be elucidated. However, investigation of the most effective IUDED is difficult because of the large number of women needed.
In conclusion, the results of our prospective study show that TVU is not necessary on a routine basis to monitor the position of the IUD, neither immediately after insertion nor at the recommended follow-up after 6 weeks. Clinicians with little experience are equally capable of inserting and monitoring IUD when compared with more experienced clinicians. Therefore there is no need to refer women from primary to secondary care for insertion of an IUD. This is, especially from the cost-effectiveness point of view, highly favourable. Only in the case of clinical suspicion of inadequate location of the IUD, as a result of the gynaecological interview and examination, may the use of TVU be beneficial and cost-effective since this decreases the number of unnecessarily removed IUD.
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Submitted on May 6, 2003; accepted on July 9, 2003.