The effect of collection method on urinalysis results in women with pelvic organ prolapse.
Key Words: Midstream clean catch, catheterization, pelvic organ prolapse, urinalysis, female.
The midstream clean-catch (MSCC) technique is currently the preferred method of urine collection in the outpatient setting. Historically, to minimize contamination from the vaginal area and skin, urethral catheterization was routinely used to obtain urine specimens. In 1958, the first studies were published revealing the MSCC technique to be equivalent to urethral catheterization (Beeson, 1958; Boshell & Sanford, 1958). Walter and Knopp (1989) have confirmed this finding, and as a result, the MSCC technique became the standard for outpatient urine collection.
Pelvic organ prolapse is a growing problem worldwide, with a reported prevalence of up to 50% in parous women (Digesu, Chaliha, Salvatore, Hutchings, & Khullar, 2005). Patients with urogenital prolapse commonly present with lower urinary tract symptoms, such as incontinence, frequency, urgency, and obstructed voiding. These patients often undergo urinalysis to rule out infection and microscopic hematuria. Regardless of the extent of urogenital prolapse, MSCC has continued to remain the de facto standard for outpatient urine collection. There are no previously published studies evaluating the accuracy of the MSCC technique in women with urogenital prolapse. The primary objective of this study was to determine the equivalence between MSCC and catheterized urine specimens in women with urogenital prolapse to or beyond the hymen. We hypothesize that the MSCC technique does not yield accurate urinalysis results in women with advanced pelvic organ prolapse.
Using a prospective study design, data were collected from 72 consecutive women who presented to an outpatient urogynecologic center with advanced urogenital prolapse between May and September 2011. Institutional Review Board (IRB) approval was obtained, and written consent was secured from all participants prior to the initiation of any study-related activity. Each potential participant provided a detailed health history, underwent a physical examination, and completed the Pelvic Organ Prolapse Quantification (POP-Q) evaluation. POP-Q is a standardized system used to measure the extent of pelvic organ prolapse in patients undergoing urogynecologic evaluation for prolapse. POP-Q has been proven to have strong reproducibility among observers. One study showed statistically significant correlations (p = 0.0008 to < 0.0001) between observers on all nine measurements of the POP-Q evaluation (Hall et al., 1996).
Patients were screened for eligibility by using inclusion and exclusion criteria. If eligible to enroll, the nature and purpose of the study was explained to the patient. Inclusion criteria included being over the age of 18 years, having the ability to provide informed consent, and where the leading edge of their prolapse was to or beyond the vaginal hymen on pelvic examination, this correlates to Stage 2 or greater pelvic organ prolapse. Individuals who were pregnant, or who had a pessary, history of pelvic radiation, or any impairment preventing the ability to perform the MSCC technique were excluded from study participation. Written informed consent was obtained from all 72 potential patients who were solicited for study participation.
No patient refused to be part of the study. All participants were given instructions on how to perform the MSCC technique, and bactericidal wipes were provided. Each participant used the wipes to cleanse the urethra, vagina, and perineum from front to back; spread the labia; and collect a midstream sample into a sterile container. Participants then underwent sterile straight catheterization, and both urine samples were sent for microscopic urinalysis (UA). The urethra was cleansed with antiseptic solution, and a sterile catheter was placed into the urethra and bladder to obtain a urine specimen. There was one clinician who performed sterile straight catheterization. For each participant, the MSCC specimen was compared to the catheterized specimen for all components of the microscopic UA.
The primary outcome variables were the components of a urinalysis. The critical measurements were white blood cell count (WBC), red blood cell count (RBC), bacteria, leukocyte esterase, squamous epithelial cells, and nitrites. WBC, RBC, bacteria, leukocytes esterase, and squamous epithelial cells were ordinal variables. Nitrite was treated as a binary outcome (positive or negative).
The study sample size was 72, which is based on the following argument. According to Cicchetti and Fleiss (1977), the minimal sample size required for the valid application of weighted kappa is 2k2, where k is the number of categories. This formula ensures that the calculation, confidence intervals, and p-values. Agreement between urine collection techniques was calculated using weighted and Cohens' kappa (k) for ordinal and binary outcomes respectively. The above analysis was repeated and stratified by type of pelvic organ prolapse; namely, anterior, posterior, and apical.
Significant agreement was determined if the kappa was greater than or equal to 0.75, in accordance with Fleiss (1981). The Wilcoxon signed-rank (WSR) test was used as a paired difference test between urine collection techniques. All analysis was conducted in SAS Version 9.2 (Cary, NC: SAS Institute, 2002-2008).
The total sample size was 72. The age range was 31 to 89 years, with a mean age of 60.3 years (SD = 12.2 years). Of the 72 participants, 65 (90.3%), 28 (38.9%), and 46 (63.9%) had prolapse in the anterior, posterior, and apical groups, respectively.
Agreement (kappa statistic results) between urine specimens obtained from the MSCC versus catheterization technique is demonstrated for each component of the urinalysis in Table 1. As shown in Table 1, there was no significant agreement between MSCC and catheterized specimens when evaluating bacteria, WBC, leukocyte esterase, RBC, and squamous epithelial cells regardless of the type of prolapse present. The urinalysis result with the highest level of agreement between the MSCC technique and catheterization was nitrites (k = 1.0000, perfect agreement). The urinalysis result with the lowest level of agreement between clean catch and catheterization was squamous epithelial cells [k = 0.0607).
Based on the WSR test, a significant association between urinalysis method and leukocyte esterase, squamous epithelial cells, and WBC was established. Urine specimens obtained by the MSCC technique had significantly higher levels of leukocyte esterase (p < 0.0001), squamous epithelial cells (p < 0.0033), and WBC [p < 0.0001) as compared to catheterized specimens. There was no significant association between urinalysis method and bacteria or RBC.
These data suggest that the method of urine collection affects urinalysis results in women with advanced urogenital prolapse. There was inadequate agreement between collection techniques on all major components of a microscopic UA with the exception of nitrites. Urine collected via the MSCC technique had significantly higher levels of leukocyte esterase, squamous epithelial cells, and WBC compared to catheterized specimens.
Previous studies demonstrate the clinical equivalence of the MSCC technique to catheterization in women undergoing urinalysis (Chen, Parviainen, & Jeyabalan 2008; Guss et al., 1985; Knopp & Walter, 1989). MSCC and catheterized specimens were compared in a study on pregnant women being evaluated for preeclampsia (Chen et ah, 2008). In this study, the investigators identified a significant correlation with a correlation coefficient of 0.897 [p < 0.001) between specimens and concluded that routine catheterization was not necessary in these women. Our study differs from the prior literature in that our patient population has advanced urogenital prolapse extending to or beyond the vaginal hymen. There are minimal data on the manner in which urogenital prolapse affects the accuracy of urine collection techniques. Our findings support the hypothesis that the MSCC technique does not yield accurate UA results in women with advanced urogenital prolapse.
A potential limitation of this study is the sample size. Sample size and power calculations for the kappa statistic in a kx k table (where k > 2) are complex and not readily accessible via available statistical software. The calculation is further complicated in the case of weighted kappa, which was the planned method in this study. A sample size of 72 was calculated as the sample size required for the valid application of weighted kappa based on the formula derived from Cicchetti and Fleiss (1977).
Another limitation of our study is the possibility of measurement bias. Although participants were given standard instructions for the MSCC technique, it is possible that the collection may have been performed more carefully in the context of a clinical trial compared to usual routine care. However, if this occurred, we would expect more agreement between techniques because patients would be wiping more carefully, leading to less contamination. Despite the potential for more careful cleansing in the setting of a clinical trial, there was insignificant agreement between techniques for all major components of the UA besides nitrites. In our study, urine cultures were performed on the catheterized specimens only. This was due to elevated costs and our hypothesis that MSCC urine specimens were not accurate in women with advanced prolapse. We hypothesized that the MSCC technique would yield inaccurate UA results in women with advanced urogenital prolapse due to contamination of the specimen by the prolapsed tissue. When urogenital prolapse extends to or beyond the hymen, we believe there is a high likelihood that urine runs over the prolapsed vaginal tissue as it exits the urethra. This would lead to contamination of a clean catch urine specimen. In addition, advanced urogenital prolapse has been shown to induce bladder outlet obstruction secondary to mechanical urethral kinking or compression by the prolapse (Richardson, Bent, & Ostergard, 1983; Romanzi, Chaikin, & Blaivas, 1999). This compression can potentially alter the urinary stream making a clean catch specimen more difficult to obtain.
Our results show inadequate agreement between urine collection techniques in women with advanced prolapse. Based on our findings, we recommend sterile straight catheterization as the technique for urine collection in women with urogenital prolapse to or beyond the hymen.
To determine whether the midstream clean catch technique yields accurate urinalysis results in women with advanced urogenital prolapse.
This prospective study included women with pelvic organ prolapse to or beyond the vaginal hymen and who were being treated at an urogynecologic center. Midstream clean catch and catheterized urine specimens were obtained for each patient, and samples were compared by microscopic urinalysis. Agreement between techniques was calculated using weighted and Cohen's kappa (k).
Seventy-two patients with a mean age of 60.3 years were evaluated. There was no significant agreement between clean catch and catheterized specimen when evaluating bacteria (k= 0.44), white blood cells (k= 0.44), leukocyte esterase (k= 0.33), red blood cells (k= 0.23), and squamous epithelial cells (k = 0.06). Urine specimens obtained via midstream clean catch technique had significantly higher leukocyte esterase (p < 0.0001), squamous epithelial cells (p < 0.0033), and white blood cells (p < 0.0001) compared to catheterized specimens.
There was inadequate agreement between collection techniques on all major components of a microscopic urinalysis with the exception of nitrites. These results indicate that the midstream clean catch does not yield accurate urinalysis results in women with advanced urogenital prolapse.
Level of Evidence--II (Polit & Beck, 2012)
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Boshell, B.R., & Sanford, J.P. (1958). A screening method for the evaluation of urinary tract infections in female patients without catheterization. Annals of Internal Medicine, 48(5), 1040.
Chen, B.A., Parviainen, K., & Jeyabalan, A. (2008). Correlation of catheterized and clean catch urine protein/creatinine ratios in preeclampsia evaluation. Obstetrics S' Gynecology, 112(3), 606-610. doi:10.1097/AOG.0b 013e3181827c89
Cicchetti, D.V., & Fleiss, J.L. (1977). Comparison of the null distributions of weighted kappa and the C ordinal statistic. Applied Psychological Measurement, 1(2), 195-201. doi:10. 1177/014662167700100206
Digesu, G.A., Chaliha, C., Salvatore, S., Hutchings, A., & Khullar, V. (2005). The relationship of vaginal prolapse severity to symptoms and quality of life. BJOG: An International Journal of Obstetrics &? Gynaecology, 112(7), 971-976. doi:10.1111/j.1471-0528. 2005.00568.x
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Interobserver and intraobserver reliability of the proposed International Continence Society, Society of Gynecologic Surgeons, and American Urogynecologic Society pelvic organ prolapse classification system. American Journal of Obstetrics and Gynecology, 175(6), 1467-1471.
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Richardson, D.A., Bent, A.E., & Ostergard, D.R. (1983). The effect of uterovaginal prolapse on urethrovesical pressure dynamics. American Journal of Obstetrics and Gynecology, 146(8), 901-905.
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Shalom, D.F., Liao, C., O'Shaughnessy, D.L., & Winkler, H.A. (2014). The effect of collection method on urinalysis results in women with pelvic organ prolapse. Urologic Nursing, 34(3), 128-130, 138. doi:10.7257/1053-816X.2014.34.3.128
Dara F. Shalom, MD, is an Attending Physician, Division of Female Pelvic Medicine and Reconstructive Surgery, North Shore-LIJ Health System, Manhasset, NY.
Christina Liao, MD, is a Fellow, Female Pelvic Medicine and Reconstructive Surgery, Harbor-UCLA Medical Center, Torrance, CA.
Danielle L. O'Shaughnessy, MD, is a
Resident, Department of Obstetrics and Gynecology, Hofstra North Shore-LIJ School of Medicine, Manhasset, NY.
Harvey A. Winkler, MD, is Co-Chairman, Division of Female Pelvic Medicine and Reconstructive Surgery, North Shore-LIJ Health System, Manhasset, NY.
Table 1. Agreement Between Clean Catch and Catheterized Urine Specimens in Women with Advanced Urogenital Prolapse Overall Anterior Posterior Apical Urinalysis (n = 72) (n = 65) (n = 28) (n = 46) Nitrite 1.0000 -- -- -- Bacteria 0.4453 0.4371 0.3514 0.4670 White blood cells 0.4478 0.4241 0.6448 0.5645 Leukocyte esterase 0.3330 0.2862 0.4928 0.3956 Red blood cells 0.2321 0.2894 0.5281 0.1948 Squamous epithelial 0.0607 0.0792 0.1250 0.0636 cells
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|Author:||Shalom, Dara F.; Liao, Christina; O'Shaughnessy, Danielle L.; Winkler, Harvey A.|
|Date:||May 1, 2014|
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