The treatment of benign prostatic hyperplasia and the definition of bladder-outlet obstruction has preoccupied urologists and researchers in recent years. Bladder-outlet obstruction can be defined only by pressure-flow measurement. Various methods of analysis of pressure-flow data have been proposed. The Abrams-Griffiths nomogram is an easy method of classifying these data to distinguish between the presence or absence of obstruction. Using the values for the maximal flow and the corresponding voiding detrusor pressure a point can be plotted on the nomogram that determines whether the bladder outlet is obstructed, unobstructed, or equivocally obstructed. For those that fall in the equivocal zone, further criteria for the mean slope of the pressure-flow plot and the minimal voiding detrusor pressure are used to determine whether there is obstruction or not. The nomogram's prognostic value in predicting the outcome of prostatectomy has been studied and found to be excellent. The Abrams-Griffiths nomogram can be modified by assigning an Abrams-Griffiths number to each set of pressure-flow data. This number is easy to calculate and use and gives a continuous variable that can be used to evaluate the effects of therapy. Although the Abrams-Griffiths nomogram and number are somewhat simplistic, none of the more complex methods of pressure-flow analysis have been shown to be better predictors of treatment outcome to date.

BackgroundAlthough several previous studies have assessed the association of fine particulate matter (PM2.5) exposure during pregnancy with preterm birth, the results have been inconsistent and remain controversial. This meta-analysis aims to quantitatively summarize the association between maternal PM2.5 exposure and preterm birth and to further explore the sources of heterogeneity in findings on this association.MethodsWe searched for all studies published before December 2014 on the association between PM2.5 exposure during pregnancy and preterm birth in the MEDLINE, PUBMED and Embase databases as well as the China Biological Medicine and Wanfang databases. A pooled OR for preterm birth in association with each 10 μg/m3 increase in PM2.5 exposure was calculated by a random-effects model (for studies with significant heterogeneity) or a fixed-effects model (for studies without significant heterogeneity).ResultsA total of 18 studies were included in this analysis. The pooled OR for PM2.5 exposure (per 10 μg/m3 increment) during the entire pregnancy on preterm birth was 1.13 (95 % CI = 1.03–1.24) in 13 studies with a significant heterogeneity (Q = 80.51, p < 0.001). The pooled ORs of PM2.5 exposure in the first, second and third trimester were 1.08 (95 % CI = 0.92–1.26), 1.09 (95 % CI = 0.82–1.44) and 1.08 (95 % CI = 0.99–1.17), respectively. The corresponding meta-estimates of PM2.5 effects in studies assessing PM2.5 exposure at individual, semi-individual and regional level were 1.11 (95 % CI = 0.89–1.37), 1.14 (95 % CI = 0.97–1.35) and 1.07 (95 % CI = 0.94–1.23). In addition, significant meta-estimates of PM2.5 exposures were found in retrospective studies (OR = 1.10, 95 % CI = 1.01–1.21), prospective studies (OR = 1.42, 95 % CI = 1.08–1.85), and studies conducted in the USA (OR = 1.16, 95 % CI = 1.05–1.29).ConclusionsMaternal PM2.5 exposure during pregnancy may increase the risk of preterm birth,but significant heterogeneity was found between studies. Exposure assessment methods, study designs and study settings might be important sources of heterogeneity, and should be taken into account in future meta-analyses.Electronic supplementary materialThe online version of this article (doi:10.1186/s12884-015-0738-2) contains supplementary material, which is available to authorized users.

Objective To assess the variability of free‐flow studies in men presenting with lower urinary tract symptoms (LUTS) suggestive of benign prostatic obstruction (BPO) and to determine the sensitivity, specificity and predictive values of consecutive measurements of maximum flow rate for the presence of bladder outlet obstruction (BOO) at several threshold values. Patients and methods The value of multiple free‐flow studies was assessed in 165 men presenting with LUTS suggestive of BPO. Each patient was requested to void four times into a uroflowmeter and the voided volume and post‐void residual urine volume (PVR) were also measured. The variability of the maximum flow rate (Qmax ), voided volume and PVR between consecutive voids was assessed. In addition, the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of various thresholds of Qmax for the presence of BOO were calculated for each consecutive void. Results The mean Qmax on void 1 was 10.2 mL/s and the mean maximum value for Qmax between voids 1 and 2 was 12.5 mL/s. For voids 1, 2 and 3, the mean maximum Qmax was 13.9 mL/s and for voids 1 to 4 it was 15.2 mL/s. There were no significant changes in PVR among any of these voids. There was a statistically significant, although small, decrease in voided volume between voids 1 to 3 and voids 1 to 4. The specificity and PPV of Qmax for BOO increased with each subsequent void, such that using a threshold value for Qmax of 10 mL/s on the fourth void, the specificity and PPV for BOO were 96% and 93%, respectively. Conclusions There was a significant increase in Qmax with each successive void when men with LUTS suggestive of BPO performed multiple free‐flow measurements and consequently, single free‐flow measurements substantially underestimated the maximum Qmax that these patients achieved. The specificity and PPV of Qmax for BOO can be improved considerably by performing multiple free‐flow studies and by carefully selecting an appropriate threshold value (although whether pressure‐flow studies are unnecessary will depend on what level of specificity and PPV is deemed acceptable in clinical practice). These findings should be considered if free‐flow studies are to be used as the basis for deciding the clinical management of men with LUTS and may be particularly useful for urologists with limited facilities for pressure‐flow studies.

Editorial group: Cochrane Gynaecology and Fertility Group. Publication status and date: New search for studies and content updated (no change to conclusions), published in Issue 7, 2019.