Search PubMed⌕ Search

Biomedical subjects

J W Ross

Publications and source records attributed to J W Ross.

At least 37 records · Page 2Linked to original sources
PubMed1998

The accuracy of laboratory measurements in clinical chemistry: a study of 11 routine chemistry analytes in the College of American Pathologists Chemistry Survey with fresh frozen serum, definitive methods, and reference methods.

CONTEXT: Better procedures are needed whereby national proficiency testing survey providers can assess and improve the accuracy of laboratory measurements in clinical chemistry. SETTING: The 1994 College of American Pathologists Comprehensive Chemistry Survey. DESIGN: This study of matrix effects and the accuracy of laboratory measurements for 11 analytes linked the logistics of the Survey to definitive methods at the National Institutes of Standards and Technology, reference methods at the Centers for Disease Control and Prevention, proficiency testing materials, and a fresh frozen serum sample. The data were analyzed with a statistical model of laboratory measurements. RESULTS: (1) Matrix biases affected the results reported from 69% of the 644 peer group/survey specimen pairs evaluated. (2) Because of matrix biases, the reference value was the correct target value only 32% of the time; thus, the traceability established by definitive method and reference method value assignments on Chemistry Survey specimens did not assure accuracy on patient samples. (3) In contrast to matrix biases, the error caused by random matrix effects with proficiency testing samples was about the same as that caused by random specimen effects with fresh frozen serum, and both were less than within-run random analytic error. (4) Calibration biases occurred in 73% of the 180 peer groups evaluated, and, after matrix biases were removed, the total variance of interlaboratory measurements was due to peer group calibration bias (48%), within-peer-group random calibration error (31 %), within-run random error (14%), and random specimen effects (7%). CONCLUSIONS: An opportunity exists to improve method calibration accuracy in clinical chemistry. With improved design, national proficiency testing surveys can monitor and help reduce method calibration error by converting reported survey results to a true accuracy base that predicts accuracy on patient samples. For medical purposes, the correct target values on artificial (matrix-modified) chemistry materials are reference values adjusted for the matrix bias of each peer group. Matrix biases estimated by the use of fresh frozen serum can be used as factors to transfer the accuracy of definitive methods from artificial reference materials to patient samples.

Bias↗
PubMed1997

Apical vault repair, the cornerstone or pelvic vault reconstruction.

Pelvic organ prolapse remains a difficult problem for pelvic reconstructive surgery. Before new surgical procedures can be developed a good understanding of pelvic anatomy is necessary. It is widely held that the etiology of pelvic organ prolapse is secondary to stretch neuropathy following childbirth and chronic cough or constipation. Several transvaginal and transabdominal procedures have been developed over the years. With the increasing use of laparoscopy, a new variation on existing culdeplasty techniques has been developed. Following anatomical principles, the apical vault repair reestablishes the pericervical ring at the vaginal apex. The incorporation of pubocervical fascia, uterosacral-cardinal ligament and the rectovaginal fascia provides a strong anchor for the vaginal apex. In addition, the repair should help prevent future transverse cystocele, rectocele, enterocele and apical vault prolapse. Early outcome studies suggest that the apical vault repair should be used routinely with laparoscopic urethropexy, laparoscopic hysterectomy and the repair of pelvic organ prolapse. Good apical vault support is considered the cornerstone of pelvic reconstruction.

Female↗
PubMed1997

Self-esteem and adiposity in black and white girls: the NHLBI Growth and Health Study.

PURPOSE: Obesity is assumed to have a negative impact on self-esteem because of the associated social stigmatization in Western society. Studies of the psychological effect of obesity in children are inconclusive and limited, particularly pertaining to minority populations. Most studies have assessed global rather than domain-specific measures of self-esteem and hence, may have lacked specificity to detect impairment of certain aspects of self-esteem most closely associated with obesity. The purpose of this study is to examine the effect of adiposity and other environmental factors on measures of perceived competence and self-adequacy in 2205 black and white girls aged 9-10 years. METHODS: Domain-specific measures of self-esteem were studied by race and degree of adiposity, using Harter's "Self-Perception Profile for Children". Three Harter scales deemed more relevant to obesity (social acceptance (SA), physical appearance (PA), and global self-worth (GSW)) were selected for univariate and multivariate linear regression models to examine relationships between self-esteem level and adiposity (measured by the sum of triceps, subscapular, and suprailiac skinfolds (SSF)), race, pubertal maturation, and parental education. The relationship between adiposity and Harter scores was further examined with LOESS curves and also by comparing the mean scores of each quintile of SSF by race, as well as inter-quintile differences within race. RESULTS: Adiposity in general impacted negatively on the scores of all three selected Harter scales. There was also racial variation in the relationship between the scores and adiposity, with the magnitude of the effect somewhat less in black girls. White girls exhibited a significant inverse relationship between SSF and SA scores while, in striking contrast, there was no variation in scores in black girls across all ranges of adiposity. Although there was a significant inverse relationship between adiposity and PA and GSW in both groups, the slope was steeper in white girls, particularly at higher ranges of SSF. Non-linearity in the relationship between SSF and the scores was seen in SA and PA scales. CONCLUSIONS: The present study demonstrated a significant negative association between adiposity and the level of self-esteem in girls as young as 9 to 10 years. There were also intriguing racial differences in the selected domains of esteem. These results may help better understand cultural differences regarding the psychological impact of obesity and could be used to formulate appropriate strategies for public health policy.

Black or African American↗
PubMed1997

Techniques of laparoscopic repair of total vault eversion after hysterectomy.

STUDY OBJECTIVE: To diagnose total pelvic vault eversion and develop surgical techniques for laparoscopic pelvic reconstruction in women after hysterectomy. DESIGN: Prospective study. SETTING: Regional hospital. PATIENTS: Nineteen women with total pelvic vault eversion and other pelvic defects after hysterectomy. INTERVENTIONS: All patients had a complete history and physical examination, and complete multichannel urodynamics. Cystocoele, rectocele, enterocele, and vault eversion were graded on a scale of 1 to 4. Posterior vaginal repair, sacral colpopexy, modified culdoplasty, paravaginal repair, and Burch urethropexy were performed laparoscopically according to the vault defects present. All patients had repeat transperineal ultrasound, cough stress test, urodynamic study, and vault examination 6 weeks and 1 year postoperatively. MEASUREMENTS AND MAIN RESULTS: Extensive diagnostic and grading criteria were used to determine which surgical repairs would result in the most anatomic outcome. Before surgery, 6 patients had complaints of urinary stress incontinence and 11 other were identified with the pessary test. All 19 patients underwent a sacral colpopexy, modified culdoplasty, and Burch urethropexy. Six paravaginal and 13 posterior vaginal repairs were performed. At 6 weeks, two women had detrusor instability that resolved spontaneously; no patients had stress incontinence or pelvic prolapse. At 1 year, one patient had mild genuine stress incontinence (93% cure rate) and none had vault eversion (100% cure rate). Two patients had grade 1 cystocele; one had grade 1 and two grade 2 rectoceles. CONCLUSION: Initial results of laparoscopic repair of total pelvic vault eversion are comparable to those of other surgical approaches. Careful anatomic evaluation of the different defects, together with urodynamic studies, are necessary in treating this difficult disorder.

Adult↗
PubMed1996

Pharmacoeconomics of Pneumocystis carinii pneumonia in HIV-infected and HIV-noninfected patients.

Despite the proven effectiveness of Pneumocystis carinii pneumonia (PCP) prophylaxis in both HIV-infected and HIV-noninfected patients, PCP remains an important cause of serious pulmonary infection. Because PCP is a frequent event requiring inpatient admission at our institution, we conducted a study to define the pharmacoeconomics of this infection and the incidence of adverse events associated with anti-PCP therapy. In a retrospective review, 133 patients (101 HIV-positive, 32 HIV-negative) with documented PCP were identified. Significant differences in age, initial arterial oxygen tension (paO2), intensive care unit admission and mortality were evident between HIV-infected and non-HIV-infected patients; however, there were no differences in the duration of hospitalisation or the duration of anti-PCP therapy. The incidence of biochemical abnormalities was similar between the groups. Leucopenia occurred at an incidence of 52 and 31%, while thrombocytopenia occurred at a rate of 7 and 44%, in HIV-positive and HIV-negative patients, respectively. Drug toxicity or treatment failure necessitated a change of therapy in 43% of HIV-positive and 59% of HIV-negative patients. PCP treatment cost, pharmacy cost, hospital cost and net loss (i.e. the difference between hospital cost and reimbursement) were all significantly greater in HIV-negative than in HIV-positive patients. The duration of anti-PCP therapy and the hospital cost for cotrimoxazole (trimethoprim-sulfamethoxazole)- and pentamidine-treated patients were similar, although the treatment cost and pharmacy cost were statistically different in favour of cotrimoxazole. Overall, cotrimoxazole is an inexpensive treatment option. However, the high incidence of adverse events attributed to this agent often necessitates a change to a more costly therapy.

AIDS-Related Opportunistic Infections↗
PubMed1996

Laboratory precision performance: state of the art versus operating specifications that assure the analytical quality required by clinical laboratory improvement amendments proficiency testing.

OBJECTIVE: To estimate the percent of laboratories with precision performance sufficient to satisfy the operating specifications and guarantee the quality required by the proficiency testing criteria defined by the Clinical Laboratory Improvement Amendments of 1988 (CLIA). DESIGN: Cumulative distributions that describe state-of-the-art laboratory imprecision were obtained for 1500 laboratories participating in the 1990 College of American Pathologists Quality Assurance Service. Allowable imprecision was estimated from the x-intercepts of charts of operating specifications prepared for commonly used single and multirule quality control procedures having two to four control measurements per run. MAIN OUTCOME MEASURE: The derived values for allowable imprecision were imposed on the cumulative distributions to obtain graphical estimates of the percent of laboratories satisfying the operating specifications. RESULTS: Up to 28% of laboratories achieve the imprecision allowable for albumin, up to 64% for total bilirubin, 52% for calcium, 35% for chloride, 48% for cholesterol, 28% for cortisol, 84% for creatinine, 9% for digoxin, 61% for glucose, 64% for high-density lipoprotein cholesterol, 88% for hemoglobin, 95% for potassium, 66% for total protein, 18% for sodium, 29% for thyroxine, 87% for triglycerides, 35% for urea nitrogen, and 81% for uric acid. CONCLUSION: Improvements in precision are still needed for many laboratory tests to assure the analytical quality required by the CLIA proficiency testing total error criteria.

Blood Chemical Analysis↗
PubMed1995

Experience with a once-daily aminoglycoside program administered to 2,184 adult patients.

Once-daily aminoglycoside (ODA) regimens have been instituted to maximize bacterial killing by optimizing the peak concentration/MIC ratio and to reduce the potential for toxicity. We initiated an ODA program at our institution that utilizes a fixed 7-mg/kg intravenous dose with a drug administration interval based on estimated creatinine clearance: > or = 60 ml/min every 24 h (q24h), 59 to 40 ml/min q36h, and 39 to 20 ml/min q48h. Subsequent interval adjustments are made by using a single concentration in serum and a nomogram designed for monitoring of ODA therapy. Since initiation of the program, 2,184 patients have received this ODA regimen. The median dose was 450 (range, 200 to 925) mg, while the median length of therapy was 3 (range, 1 to 26) days. The median age of the population was 46 (range, 13 to 97) years. Gentamicin accounted for 94% of the aminoglycoside use, and the majority (77%) of patients received the drug q24h. The 36-, 48-, and > 48-h intervals were used for 15, 6, and 2% of this population, respectively. Three patients exhibited clinically apparent ototoxicity. Twenty-seven patients (1.2%) developed nephrotoxicity (the Hartford Hospital historical rate is approximately 3 to 5%) after a median of 7 (range, 3 to 19) days of therapy. On the basis of a prospective evaluation of 58 patients and follow-up of additional patients via clinician reports, we have noted no apparent alterations in clinical response with our ODA program. This ODA program appears to be clinically effective, reduces the incidence of nephrotoxicity, and provides a cost-effective method for administration of aminoglycosides by reducing ancillary service time and serum aminoglycoside determinations.

Adolescent↗
PubMed1995

Analytic goals, concentration relationships, and the state of the art for clinical laboratory precision.

We analyzed the College of American Pathologists' Quality Assurance Service 1990 database of 1500 clinical laboratories to evaluate concentration relationships and the state of the art for the precision of 37 analytes. We compared these data to previously reported Quality Assurance Service precision performance data from 1974 through 1980. The general trend of decreasing average long-term, within-method, within-laboratory coefficients of variation continues. However, among 24 routine chemical and therapeutic drug monitoring tests observed for 11 to 16 years, 11 showed no evidence of continuous improvement in precision. The 1990 average coefficients of variation usually exceeded analytic goals modeled by clinical responses when these models assumed that variability in test results arises solely from the analytic performance of the method. In contrast, they usually did not meet goals that take into account the presence of biologic factors among the sources of test variation. Notable exceptions are the average coefficients of variation for cholesterol and triglycerides, which markedly decreased during the National Cholesterol Education Program initiatives of the 1980s. Continuous improvement of precision in disciplines dominated by relatively mature automated methods may not be the norm unless structure and direction are provided by appropriate and accepted analytic goals.

Humans↗
PubMed1995

Evaluating lyophilized human serum preparations for suitability as proficiency testing materials for high-density lipoprotein cholesterol measurement.

OBJECTIVE: To evaluate the suitability of various commercial preparations for use by the College of American Pathologists as survey materials in assessing high-density lipoprotein cholesterol measurement performance. DESIGN: Lyophilized human serum preparations from six vendors (vendors A through F) were evaluated to determine which material(s) best mimicked the commutability of fresh human serum. Two freshly collected unfrozen pools prepared from donor specimens were analyzed concurrently with the vendor materials to identify sources of variation and possible matrix bias. Each material was evaluated using 5 common precipitation reagents (phosphotungstate-magnesium, phosphotungstic acid, dextran sulfate [50K and 500K], and heparin-manganese). To evaluate how each reagent separates lipoproteins in each material, the lipoprotein separation patterns were profiled using high-pressure liquid chromatography and compared with separation patterns observed for the fresh human serum pools. MAIN OUTCOME MEASURES: Similarities in performance characteristics of vendor material(s) were compared with fresh human serum. RESULTS: Two of the six materials gave separation profiles for the lipoproteins similar to the typical patterns observed for human serum. Material from vendor B showed the best commutability across all of the precipitation reagents and had the best combination of low overall variability (10% for level 1 and 9.4% for level 2) and minimal concentration differences among reagents. CONCLUSIONS: Vendor B was selected by the College of American Pathologists to provide materials for use in assessing performance of lipid and lipoprotein testing in the 1994 Comprehensive Chemistry Surveys. This study demonstrates the great variability that different vendor preparations introduce into the measurement of high-density lipoprotein cholesterol. It also emphasizes the effort required to evaluate the suitability of processed materials for use in proficiency testing.

Analysis of Variance↗
PubMed1995

The stability of survey-assigned assay values when surveyed control materials are used in a daily interlaboratory quality control program. The College of American Pathologists Chemistry Survey--Quality Assurance Service shared pool experience.

Two pools of lyophilized human control serum, distributed as challenges for the 1990 and 1991 College of American Pathologists Comprehensive Chemistry Surveys were employed consecutively as two-level, daily, quality control materials in College of American Pathologists Quality Assurance Service Regional Quality Control programs. Because the Chemistry Survey and Quality Assurance Service use identical method codes and the materials are essentially stable, the variation of differences among Chemistry Survey and Regional Quality Control assay values is a sensitive measure of both the variation of accuracy among calibrator-assigned values and of the matrix response among calibrator/reagent lots following the time of initial Chemistry Survey assay. In the two cycles of data comparison, the Regional Quality Control means for the assay values of 15 stable routine chemistry analytes showed no statistically significant differences from the initial Chemistry Survey for 295 of 361 analyte-method combinations studied 16 months later. Statistically significant changes between Chemistry Survey assay values and Regional Quality Control means most often occurred with closed rather than with open analytic systems and were predominantly in the same direction at both concentration levels. The magnitude of bias difference was usually less than the average within-laboratory standard deviation for the same analyte concentration. Of 64 analyte-pool combinations studied, a single instance of probable analyte instability was noted, ie, decreasing level I glucose during the first cycle. Our findings strongly support the usefulness of Chemistry Survey-assigned target values to help strengthen the intralaboratory accuracy base. They also point out the need for and the utility of Regional Quality Control-recalculated interlaboratory means to supplement assay values assigned at the time a control pool was put into use.

Chemistry, Clinical↗