knowledge. Recurrent stone-formers are significantly less likely to be colonized with OF than controls, but this appears to be due to antibiotic use. Studies in animals and human subjects show that colonization of the gut with OF can decrease urinary oxalate levels. However, it remains to be determined whether colonization with OF can affect stone disease. Reliable methods are needed to detect and quantify colonization status and to achieve durable colonization. New information about oxalate transport mechanisms raises hope for pharmacological manipulation to decrease urinary oxalate levels. In addition, probiotic use of lactic acid bacteria that metabolize oxalate might provide a valid alternative to OF.
OBJECTIVE
To assess the magnitude of variability among 11 formulae for human body surface area (BSA) and then among eight for plasma volume (PV), as used to represent physiological indices for body metabolism, drug dosages and body fluid management, and to evaluate the potential cumulative effect of variance inflation with prostate‐specific antigen (PSA) mass as an endpoint.
PATIENTS AND METHODS
In 3020 men undergoing robotic radical prostatectomy (RRP) at the Vattikuti Urology Institute between 2001 and 2008, the variation in BSA and PV formulae was calculated, as well as PSA mass, using analysis of variance (anova), Bland‐Altman plots, linear regression, and correlation analyses.
RESULTS
For estimating BSA, anova indicated significant variance among the 11 formulae used (P < 0.001) with a between‐groups variance of 5.45. Bland‐Altman plots reported bias when the Dubois formula was compared to other BSA formulae. Furthermore the anova for PV, with BSA as a predictor, indicated significant variance among the eight formulae used (P < 0.001), with a mean between‐group variance of 444.4 and a mean inflation factor of 81.5. Scatter plots between one PV formula (Boer) and others had a good linear fit. For PSA mass, anova indicated significant variance (P < 0.001) using PV as a predictor, with a mean between‐group variance of 16 799.6 and a mean variance inflation factor of 37.8.
CONCLUSIONS
There is significant variation in the BSA calculated by commonly used formulae. This variation is carried over and further magnified in the sequential calculation of PV and PSA mass. Hence arbitrary selection of BSA and PV formulae is likely to affect inferences.
The Bladder Neck Support Prosthesis (BNSP) was used in 21 women with combined genuine stress incontinence (GSI) and detrusor instability (DI). Outcomes included frequency volume charts, pad tests, voiding cystometry and quality of life scores, up to the sixth month. Of the 21 recruits, 5 never wore the BNSP home, leaving 16 participants. A further 2 did not reach week 4 because of poor efficacy or inability to fit the device. In the 14 who reached week 4, the median number of leaks/day declined from 4.3 to 1.0 (p = 0.002). Median pad test loss fell from 53 to 7 mL (p = 0.012). Cystometry showed an increase in maximum bladder capacity (p < 0.05) and a modest reduction in severity of detrusor instability, with no evidence of outflow obstruction. Three further women discontinued because of poor efficacy (2) or a poorly fitting device (1), leaving 11 of 16 participants (69%) at week 8, when median pad test loss fell to 2 mL. The BNSP is a useful option in patients with the unfortunate combination of an unstable bladder and an incompetent urethra, but requires careful fitting and attention to detail.
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