Analysis of repeated bouts of measurements in the framework of generalized estimating equations.

We consider a longitudinal study of interstitial cystitis (IC) in women, in which the time between bouts of repeated measurements is large relative to the within-bout separation in time. Our outcome of interest is the number of nocturnal voids that we model via quasi-least squares (QLS) in the framework of generalized estimating equations (GEE). To account for potential intra-subject correlation, we directly apply a banded Toeplitz correlation structure that previously was only implemented in an ad hoc approach using GEE. We describe this structure, its appropriateness for data from the IC study, and the results of our analysis. We then demonstrate that correct specification of the underlying correlation structure versus incorrectly applying a simpler structure can prevent substantial losses in efficiency in estimation of the regression parameter. These comparisons involve the limiting values of the estimates of the correlation parameters, which are not consistent for the misspecification scenarios considered here. We therefore obtain the limiting values of the QLS estimates when the structure is incorrectly specified.

Leukocyte and bacterial counts do not correlate with severity of symptoms in men with chronic prostatitis: the National Institutes of Health Chronic Prostatitis Cohort Study.

PURPOSE: We examine whether leukocytes and bacteria correlate with symptom severity in men with chronic prostatitis/chronic pelvic pain syndrome. MATERIALS AND METHODS: All 488 men screened into the National Institutes of Health Chronic Prostatitis Cohort Study before close of recruitment on August 22, 2001 were selected for analysis. The National Institutes of Health Chronic Prostatitis Symptom Index, including subscores, were used to measure symptoms. Urethral inflammation was defined as white blood cell (WBC) counts of 1 or more (1+) in the first voided urine. Participants were classified as category IIIa based on WBC counts of 5 or more, or 10 or more (5+, 10+) in the expressed prostatic secretion, or 1+ or 5+ either in the post-expressed prostatic secretion urine (voided urine 3) or semen. Uropathogens were classified as localizing if the designated bacterial species were absent in voided urine 1 and voided urine 2 but present in expressed prostatic secretion, voided urine 3 or semen, or present in expressed prostatic secretion, voided urine 3 or semen at 2 log concentrations higher than at voided urine 1 or 2. Associations between symptoms, and inflammation and infection were investigated using generalized Mantel-Haenszel methods. RESULTS: Of all participants 50% had urethral leukocytes and of 397 with expressed prostatic secretion samples 194 (49%) and 122 (31%) had 5+ or 10+ WBCs in expressed prostatic secretion, respectively. The prevalence of category IIIa ranged from 90% to 54%, depending on the composite set of cut points. None of the index measures were statistically different (p >0.10) for selected leukocytosis subgroups. Based on prostate and semen cultures, 37 of 488 men (8%) had at least 1 localizing uropathogen. None of the index measures were statistically different (p >0.10) for selected bacterial culture subgroups. CONCLUSIONS: Although men with chronic prostatitis routinely receive anti-inflammatory and antimicrobial therapy, we found that leukocytes and bacterial counts as we defined them do not correlate with severity of symptoms. These findings suggest that factors other than leukocytes and bacteria also contribute to symptoms associated with chronic pelvic pain syndrome.

Demographic and clinical characteristics of men with chronic prostatitis: the national institutes of health chronic prostatitis cohort study.

PURPOSE: We describe the study design of the National Institutes of Health Chronic Prostatitis Cohort (CPC) study characterizing men with chronic prostatitis/the chronic pelvic pain syndrome. MATERIALS AND METHODS: All 488 men screened into the CPC study before close of recruitment on August 22, 2001 were selected for analysis. The National Institutes of Health Chronic Prostatitis Symptom Index, including subscores, was used to measure symptoms. A comprehensive history, physical examination and demographic profile were obtained from each participant. Generalized Mantel-Haenszel procedures were used to investigate baseline associations between selected factors and symptoms. RESULTS: Chronic prostatitis/chronic pelvic pain syndrome is a chronic syndrome affecting men over a wide age range. The majority of CPC study participants are white, well educated and affluent. However, lower education, lower income and unemployment were associated with more severe symptoms. Patients most frequently reported pain in the perineum and tenderness in the prostate. The highest self-reported diseases were genitourinary (55%), allergies (53%), neurological (40%) and hematopoietic, lymphatic or infectious (40%). This disease has a significant negative impact on mental and physical domains of quality of life. Almost all patients (95%) reported antimicrobial drug use. Of these 488 participants 280 (57%) reported the previous or current use of 5 or more categories of prostatitis related treatments. CONCLUSIONS: Chronic prostatitis/chronic pelvic pain syndrome is a multifactorial problem affecting men of all ages and demographics. Patients with the chronic pelvic pain syndrome have dismal quality of life and many have benefited only minimally from empirical, goal directed therapy. Long-term followup of this cohort may answer important questions on the natural treated history of this syndrome.