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PubMed1998

Effects of hydration changes on bioelectrical impedance in endurance trained individuals.

PURPOSE: The purpose of this study was to determine how differences in hydration states and ion content of hydrating fluids affected bioelectrical impedance (BI) and hydrostatic weighing (HW) measurements. METHODS: Fifteen athletic subjects aged 19-56 yr were recruited. Relative body fat (%), fat-weight (FW), and fat-free weight (FFW) were assessed using BI and HW under normal conditions (N), hypohydration (HPO), rehydration (RHY), and superhydration (SHY) states. During the RHY and SHY trial periods, subjects were hydrated with either distilled water or an electrolyte solution (ELS). HPO and SHY levels were set at 3% of each person's normally hydrated body weight. RESULTS: Comparison between the distilled water and the ELS trials indicated that hydration solution had no effect on BI or HW. Thus, the results presented are the trial means of both hydration solutions combined. Both BI and HW were shown to be highly test-retest reliable (r-values: 0.96 and 0.99, respectively). The effects of exercise induced HPO followed by RHY on body composition values indicated that HW was very stable across measurement periods while BI was not. From N to the HPO state, BI %BF declined from 14.4 +/- 5.3% to 12.3 +/- 5.3%, respectively. After RHY, BIA %BF increased to 15.5 +/- 5.8%. Similar findings occurred when subjects were superhydrated (N-BI = 13.2 +/- 5.3%; SHY-BI = 15.4 +/- 5.6%). With a comparison of the intercepts and slopes of HW and BIA for the N and SHY states, it was clear hydration status significantly affected the intercepts (HW: 0.37 vs. BI: 1.85) and not the slopes (HW: 1.00 vs BI: 0.99). As a result, a majority of all fluid changes were interpreted as FW by BI. During HPO, 82% of the weight loss was considered FW while during RHY or SHY, 128% and 85% of the water weight regain/gain was considered FW. CONCLUSION: These results indicate that BI is not a valid technique in athletes, especially when wanting to determine body composition effects of training/detraining. This study indicates that even small fluid changes such as those that occur with endurance training may be interpreted incorrectly as changes in an athlete's body fat content.

Adult↗
PubMed1990

A clinical evaluation of the Camino subdural screw and ventricular monitoring kits.

The aim of this study was to compare readings of intracranial pressure from a ventricular catheter with those obtained from a Camino catheter-tipped transducer. The Camino transducer was evaluated in two ways: firstly, when it was inserted by a subdural screw, and secondly, when it was inserted into a ventricular catheter using a ventricular monitoring kit. Data were recorded for 376 hours for the subdural screw method and for 486 hours for the ventricular monitoring kit. Average pressure readings were calculated every 5 minutes (10 half-minute values), and regression analysis was performed. For the subdural screw method, the correlation coefficient was 0.945 (gradient, 1.04; intercept, -5.51. The results from the ventricular monitoring kit showed that the correlation coefficient was 0.901 (gradient, 0.93; intercept, -0.92. The correlation between recordings of ventricular fluid pressure and the Camino recordings obtained from both subdural screw insertions and ventricular monitoring kits was good, with the subdural screw method proving more accurate and reliable in clinical use.

Brain Injuries↗
PubMed1997

How good is the slope of the second exponential for estimating 51Cr-EDTA renal clearance?

The aim of this study was to test the reproducibility of the second exponential of the plasma disappearance curve of 51Cr-EDTA and to compare it with the single slope-intercept method. The test was performed twice among 24 young healthy volunteers at an interval of 8 days and under similar physiological conditions. After the intravenous injection of 3.7 MBq of 51Cr-EDTA, four blood samples were taken between 1.5 and 4 h and combinations of two, three or all four of these were used to calculate the slope of the plasma clearance curve. The clearances rates were calculated using these slopes and the corresponding intercepts of the slopes with the y-axis. The standard deviation of the differences between the first and the second measurements was between 8 and 10% for the different clearance estimates, and between 11 and 17% for the different slope estimates, reflecting the wider variability of the slope estimate. Using the first series of measurements, the change of timing for blood sampling introduced a wider variability for the slope estimate than for the clearance estimate.

Adult↗
PubMed2000

How good is the slope on the second exponential for estimating 51Cr-EDTA renal clearance? A Monte Carlo simulation.

It has been suggested that the slope of the second exponential of the plasma disappearance curve may be used to monitor changes in renal function instead of plasma clearance calculated using the slope-intercept method. The purpose of this study was to evaluate the magnitude of error in the slope induced by errors in sampling time and in activity measurement, and to compare it with the error observed in clearance. A model of mono-exponential curves based on two blood samples, taken at 120 and 240 min, was created. Normally distributed random errors were introduced into the sampling times and activity measurements. For each setting, the random errors were successively introduced 200 times and the coefficients of variation of the calculated slopes and clearances were determined. Variable errors in slope and clearance were induced by errors in sampling time and activity measurement. In general, the observed errors in the slope were high in the case of low slope values, decreasing progressively for increasing slope values. The errors in clearance followed a different pattern: highest errors were observed in the case of very low clearance, decreasing progressively for higher clearance values and attaining the minimal value at a lambda around 0.006 min-1, which corresponds to clearance of about 90 ml.min-1. The magnitude of the errors then started to increase again for higher clearance. For a large range of clearance values, the errors in the slope were higher than the errors in clearance. The only exceptions were cases with very high clearance rates. In conclusion, clearance calculation using the slope-intercept method should be preferred to that using the slope alone for monitoring changes in renal function.

Chelating Agents↗
PubMed2004

Which single blood sample method should be used to estimate 51Cr-EDTA clearance in adolescents?

Single blood sample methods are widely used for the estimation of the glomerular filtration rate, but the methods recommended for adults are not the same as those for children. The question arises, therefore, as to which method should be used in an adolescent or young adult. The aim of this study was to compare the performance of two methods, a specific paediatric converting equation and an adult algorithm, in a group of adolescent and young adult patients. From a large database of 51Cr-ethylenediaminetetraacetic acid (51Cr-EDTA) renal clearance determinations using the two blood sample method, 598 patients, aged 1 week to 90 years, were selected. The results of the 51Cr-EDTA slope intercept clearance of the two blood sample method were used as reference. Using the paediatric algorithm, no bias was observed until the age of 40 years. Then, an increasing positive bias occurred. The standard deviation of the difference was generally less than 4 ml/min until the age of 25 years and increased gradually to reach 7 ml/min at the age of 80 years. Using the Christensen and Groth adult algorithm, the best results were observed in patients older than 50 years. With the exception of children aged less than 5 years, no systematic bias was observed. The standard deviation, however, increased gradually and reached a value of around 8 ml/min in young children. For individuals aged 15-25 years, the mean of the difference between the paediatric algorithm and the slope intercept method was -1.1 ml/min, with a standard deviation of the difference of 3.3 ml/min. For the adult algorithm, the mean of the difference was 0.3 ml/min, with a standard deviation of the difference of 7.7 ml/min. It can be concluded that, for individuals aged 15-25 years, both methods performed correctly. In this series, the paediatric method gave better results than the adult algorithm, and its use is therefore recommended.

Adolescent↗
PubMed1988

Comparison of vertical fixation disparities between essential hypertensives and matched normotensives.

Using American Optical Vectographs and a Disparometer, vertical fixation disparities and associated phorias were measured on 19 essential hypertensives and 19 matched normotensives. Subjects were matched on the basis of race, sex, age, use of tobacco, and family history of hypertension. Correlated variance comparisons of the measured associated phorias and fixation disparities, as well as calculated x and y intercepts derived from forced-duction vertical fixation disparity curves were made and a t-test for related measures was used to compare slopes. The x and y intercepts and slope data showed no significant differences between the groups. However, statistically larger measured associated phorias for the hypertensive group were found on all but one test. This suggests a relation between the magnitude of vertical associated phorias and the occurrence of essential hypertension, but the relation found was not of sufficient strength to warrant clinical application.

Adult↗
PubMed2001

A comparison of noninvasive objective and subjective measurements of the optical density of human ocular media.

BACKGROUND: It is important for both researchers and clinicians to know the spectral composition of the light that reaches the retina. With this in mind, Johnson et al. developed a quick, objective instrument called the Lens Absorption Monitor (LAM) to measure the attenuation of light by the ocular media. Using a more refined method of measuring and correcting for scatter, we compared the results of the LAM against those with a subjective method utilizing a bipartite scotopic brightness-matching procedure (BIP). METHODS: We tested 41 healthy subjects (mean age, 35.9 years) with the LAM and BIP. RESULTS: Intereye correlation coefficients for the LAM were 0.70 at 410 nm and 0.83 at both 430 and 450 nm; for BIP, intereye correlation coefficients were 0.56 at 410 nm, 0.42 at 430 nm, and 0.38 at 450 nm. For optical density as a function of age, there was no statistically significant difference between the two instruments at 410 nm in either the slope (p > 0.43) or y intercept (p > 0.75). However, at both 430 and 450 nm, there was a significant difference in both slope (p < 0.001) and y intercept (p < 0.05) for the two instruments. CONCLUSIONS: With the latest refinements, LAM density measures correlated well with BIP estimates at 410 nm, but not at 430 or 450 nm. This underscores the fact that the LAM measures the spectral density of the anterior segment, whereas the BIP method is a measure of all the ocular media except for macular pigment. The difference between these two measures is consistent with the existence of a prereceptoral, presumably intraretinal, pigment (or pigments) located outside the anatomic fovea that absorbs light at short wavelengths.

Accommodation, Ocular↗
PubMed1982

A randomized-blinded evaluation of analytical error associated with the enzyme immunoassay (EMIT) of gentamicin.

Analytical error is a potential source of inaccuracy and imprecision in the pharmacokinetic dosing of the aminoglycosides. The present study was undertaken to determine the analytical error (precision and accuracy) associated with the EMIT assay for gentamicin as it is routinely used in a clinical pharmacokinetics laboratory, and to assess what impact this error would have on estimates of pharmacokinetic model parameters. Serum samples spiked with known amounts of gentamicin were assayed over a 6-week period along with routine clinical samples by a medical technologist who was blinded with regard to the expected concentration or number of replicates of each sample. Under these conditions, the assay method had a coefficient of variation (CV) of 4.8%. When this analytical error was incorporated into a first-order, one-compartment pharmacokinetic model, the CV was 0.8% for the y intercept and 1.2% for the slope. When all measured concentrations were compared with actual values, the slope and intercept were not significantly different from the line of reference. As indicated by these data, the EMIT assay for gentamicin as it is routinely used in a clinical laboratory is both precise and accurate, indicating that analytical error is not the major source of inaccuracy in pharmacokinetic dosing of gentamicin.

Gentamicins↗
PubMed1998

Isoniazid dose adjustment in a pediatric population.

This retrospective analysis was designed to evaluate the inactivation index (I3) method used to adjust the isoniazid dose during long-term administration in a pediatric population. Before starting on antituberculosis therapy, sixty-one children received one 10 mg.kg-1 isoniazid test-dose (D). The isoniazid and acetyl isoniazid concentrations were measured by high-performance liquid chromatography on a plasma sample collected 3 hours (C3h) after administration. The patients were separated into slow and fast acetylator groups according to the metabolic ratio. The dose adjustment method using the I3 is based on the assumption that there is a linear correlation between C3h and D [C3h = (I3 x D) - 0.6] in which the slope is I3 and the Y intercept is equal to -0.6 mg.l-1. I3 was determined from a single plasma concentration determination and used to calculate the dose recommended to obtain a desired C3h equal to 1.5 micrograms.ml-1: recommended dose (mg.kg-1) = (1.5 + 0.6)/I3.I3 was significantly higher in the slow acetylator group (0.55 +/- 0.16) than in the fast one (0.26 +/- 0.13), which leads us to recommend a significantly lower dose in the slow acetylator group (4.2 +/- 1.5 mg.kg-1) than in the fast one (10.3 +/- 4.6 mg.kg-1). The data obtained in a subgroup of 21 patients who had at least three consecutive determinations of C3h after different dosages allowed us to verify that there was a linear correlation between C3h and the dose. The mean slope of the correlation lines in that subgroup was 0.61 +/- 0.25 and the 95% confidence interval of the estimated Y-intercept include the theoretical value of -0.60, which shows that our data are consistent with those previously reported in adults. The percentage of patients with a C3h plasma concentration within the expected range (1.5 +/- 0.5 micrograms.ml-1) was significantly higher (69%) in those whose dose was derived from the calculation than in the others (25%). Within each acetylator group, the range of the recommended dose varied widely, and these results emphasize the usefulness of individual dose adjustment based on the inactivation index method.

Adolescent↗
PubMed2001

Simultaneous measurement of plasma ropivacaine and bupivacaine concentrations by HPLC with UV detection.

The authors developed a high-performance liquid chromatography (HPLC) assay for the simultaneous determination of plasma ropivacaine and bupivacaine concentrations using ultraviolet (UV) detection and a simple solid-phase extraction procedure. The absolute retention times of ropivacaine, bupivacaine, and the internal standard pentycaine were 1.9, 3.0, and 5.6 minutes, respectively. The assay had a linearity of 2000 ng/mL, a sensitivity of 5 ng/mL, an average recovery of 98%, and an average day-to-day imprecision of <10% for both drugs. A patient correlation study (n = 23) using this HPLC method and an established gas chromatographic assay revealed a slope of 1.01, an intercept of -10.6 ng/mL, and a correlation coefficient of 0.99 for ropivacaine; and a slope of 0.96, an intercept of 14.7 ng/mL, and a correlation coefficient of 0.99 for bupivacaine. Of the 60 different drugs tested, only quinidine and lidocaine extracted but did not interfere with the measurement of the drugs of interest. The authors conclude that the method described here is ideally suited for the therapeutic monitoring of plasma ropivacaine and bupivacaine concentrations.

Amides↗
PubMed1989

Comparative evaluation of urographic contrast media, inulin, and 99mTc-DTPA clearance methods for determination of glomerular filtration rate in clinical transplantation.

Plasma clearance of inulin (Cin), 99mTc-DTPA (CDTPA), and urographic contrast media (CCM) were determined simultaneously in 31 patients with varying levels of renal function evaluated in the setting of affiliated cardiac and renal transplantation programs. Cin and CDTPA were calculated from the ratio of simultaneously measured plasma concentration and urine excretion rate of these test agents (UxV/P). CCM was derived from x-ray fluorescence measurement of plasma iodine (PI) content following intravenous injection of 50 ml of nonionic, low-osmolar contrast media (180 mg I/ml). Urine collections were not required for CCM determinations. No adverse reactions attributable to CM occurred in any patient, and follow-up serum-creatinine values did not differ significantly from prestudy levels. CCM determined from the rate of decline in PI between 3 hr and 4 hr following administration of contrast media ("slope-intercept" technique) [Ccm-SI] correlated closely with corresponding levels of Cin (r = .86, P less than 0.0001). and CDTPA (r = 0.89, P less than 0.0001). Mean CCM-SI/Cin and CCM-SI/CDTPA ratios for the entire study cohort were 1.09 +/- 0.06 and 1.08 +/- 0.06, respectively. CCM-SI determinations also correlated well with CCM levels derived from a single measurement of PI ("single sample" technique) made at 3 hr following injection of contrast media (r = 0.94, P less than 0.0001). Both CCM-SI and CCM determined by the "single sample" method (CCM-3 degrees SS) tended to overestimate Cin and CDTPA, however, when the latter were less than 20 ml/min/1.73 m2 (mean CCM-SI/Cin and Ccm-3 degrees SS/Cin ratios 1.36 +/- 0.14 and 1.95 +/- 1.0, respectively. Reproducibility was evaluated by paired comparison of 3-hr vs. 4-hr "single sample" CCM determinations (r = 0.99, P less than 0.0001). In addition, analysis of the variation in iodine content between duplicate specimens obtained at each of these time intervals revealed a mean ratio of 1.0 +/- 0.01 (P = NS vs. identity). Contrast clearance determination utilizing the slope-intercept method is accurate, safe, pragmatic, and more precise than serum-creatinine and endogenous-creatinine clearance for measurement of renal function in clinical transplantation.

Contrast Media↗
PubMed1998

Simple method for the estimation of absorption rate constant(ka) after oral administration.

This article describes a simple method for the estimation of absorption rate constant (ka ) after oral administration and compares the proposed method with some of the existing methods. The proposed method is based on a previous work of Urso and Aarons known as the regression method of truncated areas for the estimation of absolute bioavailability for drugs with a long elimination half-life. The following equation was used to estimate ka : Y(t) = ka. F - ka. X(t). Simple linear regression of Y(t) on X(t) results in a straight line with a slope of -ka, intercept on y-axis of ka F, and abscissa intercept F (absolute bioavailability). Different sets of plasma concentration versus time data for a hypothetical drug were generated by simulation. The estimated ka from the proposed method was compared with the Wagner-Nelson, Loo-Riegelman, and statistical moments methods. The results of this study indicated that the proposed regression method performed satisfactorily for a hypothetical drug that follows a one-compartment or two-compartment model with short or long half-life when tested under variable conditions (different absorption and elimination rate constants). The regression method of truncated areas can be used for the accurate estimation of ka for both short and long half-life drugs.

Absorption↗
PubMed2003

Novel method to quantify loss of heart rate variability in pediatric multiple organ failure.

OBJECTIVE: To develop a power-law model for measurement of heart rate variability (HRV) and to compare this model with established methods for measuring HRV in a group of children with organ failure (OF). DESIGN: Prospective, observational study. SETTING: Pediatric intensive care unit of a tertiary children's hospital. PATIENTS: A total of 104 measurements were made on 50 patients (median age, 8 months; range, 2 days to 16 yrs) and categorized into three groups according to the number of simultaneous organs failing: 0-1 OF, 2 OF, and >/=3 OF. INTERVENTIONS: Heart rate was recorded over a 5-min period when patients were hemodynamically stable. The power-law model represents a power function relating frequency distribution to magnitude of effect (in this case, squared deviation from the mean heart rate). Plotting the data on a bi-logarithmic scale produces a regression line for each measurement, described in terms of r2, slope, and x-intercept. Comparison with other HRV measures included two time-domain measures (sd of the normal R-R intervals and the square root of the mean squared differences of successive normal R-R intervals), one frequency-domain method (power spectral analysis), and one nonlinear method (detrended fluctuation analysis). MEASUREMENTS AND RESULTS: For the power-law model, patients exhibited a similar r2 of.87 (.09) (mean [sd]) and slope of -1.80 (0.29), regardless of the degree of OF. HRV could thus be described purely in terms of x-intercept, which demonstrated a left shift with increasing OF (p <.001). This was independent of age and heart rate. Loss of HRV with increasing OF was demonstrated by all methods; however, only the power-law model was able to discriminate between each OF group. Using the model, change in HRV in individual patients over successive days often concurred qualitatively with the change in OF status. CONCLUSION: The power-law model is an appropriate measure of HRV in pediatric patients, being neither age nor heart rate sensitive. Loss of HRV occurs with increasing OF; this effect was better demonstrated by the model compared with other measures of HRV.

Adolescent↗
PubMed2004

Continuous positive airway pressure delivered with a "helmet": effects on carbon dioxide rebreathing.

OBJECTIVE: The "helmet" has been used as a novel interface to deliver noninvasive ventilation without applying direct pressure on the face. However, due to its large volume, the helmet may predispose to CO2 rebreathing. We hypothesized that breathing with the helmet is similar to breathing in a semiclosed environment, and therefore the PCO2 inside the helmet is primarily a function of the subject's CO2 production and the flow of fresh gas through the helmet. DESIGN: Human volunteer study. SETTING: Laboratory in a university teaching hospital. SUBJECTS: Eight healthy volunteers. INTERVENTIONS: We delivered continuous positive airway pressure (CPAP) with the helmet under a variety of ventilatory conditions in a lung model and in volunteers. MEASUREMENTS AND MAIN RESULTS: Gas flow and CO2 concentration at the airway were measured continuously. End-tidal PCO2, CO2 production, and ventilatory variables were subsequently computed. We found that a) when CPAP was delivered with a ventilator, the inspired CO2 of the volunteers was high (12.4 +/- 3.2 torr [1.7 +/- 0.4 kPa]); b) when CPAP was delivered with a continuous high flow system, inspired CO2 of the volunteers was low (2.5 +/- 1.2 torr [0.3 +/- 0.2 kPa]); and c) the inspired CO2 calculated mathematically for a semiclosed system model of CO2 rebreathing was highly correlated with the values measured in a lung model (r = .97, slope = 0.92, intercept = -1.17, p < .001) and in the volunteers (r = .94, slope = 0.96, intercept = 0.90, p < .001). CONCLUSIONS: a) The helmet predisposes to CO2 rebreathing and should not be used to deliver CPAP with a ventilator; b) continuous high flow minimizes CO2 rebreathing during CPAP with the helmet; and c) minute ventilation and Pco2 should be monitored during CPAP with the helmet.

Adult↗
PubMed2006

An essay on measurement and factorial invariance.

BACKGROUND: Analysis of subgroups such as different ethnic, language, or education groups selected from among a parent population is common in health disparities research. One goal of such analyses is to examine measurement equivalence, which includes both qualitative review of the meaning of items as well as quantitative examination of different levels of factorial invariance and differential item functioning. OBJECTIVES: The purpose of this essay is to review the definitions and assumptions associated with factorial invariance, placing this formulation in the context of bias, fairness, and equity. The connection between the concepts of factorial invariance and item bias (differential item functioning) using a variant of item response theory is discussed. The situations under which different forms of invariance (weak, strong, and strict) are required are discussed. METHODS: Establishing factorial invariance involves a hierarchy of levels that include tests of weak, strong, and strict invariance. Pattern (metric or weak) factorial invariance implies that the regression slopes are invariant across groups. Pattern invariance requires only invariant factor loadings. Strong factorial invariance implies that the conditional expectation of the response, given the common and specific factors, is invariant across groups. Strong factorial invariance requires that specific factor means (represented as invariant intercepts) also be identical across groups. Strict factorial invariance implies that, in addition, the conditional variance of the response, given the common and specific factors, is invariant across groups. Strict factorial invariance requires that, in addition to equal factor loadings and intercepts, the residual (specific factor plus error variable) variances are equivalent across groups. The concept of measurement invariance that is most closely aligned to that of item response theory considers the latent variable as a common factor measured by manifest variables; the specific factors can be characterized as nuisance variables. CONCLUSIONS: Invariance of factor loadings across studied groups is required for valid comparisons of scale score or latent variable means. Strong and strict invariance may be less important in the context of basic research in which group differences in specific factors are indicative of individual differences that are important for scientific exploration. However, for most applications in which the aim is to ensure fairness and equity, strict factorial invariance is required. Health disparities research often focuses on self-reported clinical outcomes such as quality of life that are not observed directly. Latent variable models such as factor analyses are central to establishing valid assessment of such outcomes.

Bias↗
PubMed2005

A general equation for estimating glomerular filtration rate from a single plasma sample.

OBJECTIVES: Glomerular filtration rate (GFR) may be estimated from a single plasma sample measurement using empirical equations. This method forms the basis of international guidelines on GFR measurement. New guidelines have recently been recommended by the British Nuclear Medicine Society (BNMS). These use the slope-intercept technique in which several samples are obtained. Quality control of measurement may be achieved by comparison with the individual single-sample values. This paper compares international guideline single-sample estimates of GFR with the new BNMS method and derives an improved general single-sample equation. METHODS: GFR measurements using Tc-DTPA were performed on 180 adults and 100 children using samples at approximately 2 h and 3 h and a further 45 adults with samples at 2, 3 and 4 h. The two-sample values obtained using the BNMS guideline method were compared to one-sample estimates obtained using (1) international guidelines and (2) a new equation derived from the data. The new equation was evaluated in a further 145 subjects. RESULTS: The international guidelines technique had systematic differences between the one-sample and two-sample estimates of GFR. The new equation had minimal systematic error and reduced random error (standard error of the estimate 4.5 ml . min per 1.73 m). CONCLUSIONS: There were significant differences between GFR values obtained using the international guidelines single-sample method and the slope-intercept method described in the BNMS guidelines. The new equation described in this paper gave considerably improved agreement and is recommended if single-sample estimates are to be used as quality control for BNMS guideline measurements.

Adult↗
PubMed2003

Community-based screening and treatment for STDs: results from a mobile clinic initiative.

BACKGROUND: The persistence of syphilis and other bacterial sexually transmitted diseases (STDs) in many areas of the United States suggests that innovative approaches to controlling these diseases are needed. GOAL: To evaluate the feasibility, acceptability, and yield of mobile community-based STD screening and treatment services in high STD incidence areas. STUDY DESIGN: Free, voluntary, confidential screening and treatment for STDs were conducted in high STD incidence neighborhoods of Baton Rouge, Louisiana, using a 32-foot mobile van. Demographic and behavioral data were obtained from participants. Participants were screened for syphilis, chlamydia, and gonorrhea and were also offered HIV testing. Community attitudes toward the screening program were assessed with street-intercept surveys conducted two weeks after screening events. RESULTS: From March 1997 to August 2000, 256 community-based screening events were held. During this period, 3110 blood samples were collected for syphilis testing, of which 37 (1.2%) new cases of syphilis were identified. Of the 2807 blood samples collected for HIV testing, 70 (2.5%) were positive. Of 2229 urine samples, 185 (8.3%) tested positive for Chlamydia trachomatis and 108 (4.9%) positive for Neisseria gonorrhoeae. Of 389 street-intercept surveys, 97% of respondents thought that neighborhood STD testing was a "good" or "very good" idea. CONCLUSION: Mobile community-based STD screening and treatment are feasible, identify high positivity of STDs, and are accepted by the community as an innovative approach to STD control.

Adolescent↗
PubMed2006

Evaluation of a low-cost method, the Guava EasyCD4 assay, to enumerate CD4-positive lymphocyte counts in HIV-infected patients in the United States and Uganda.

OBJECTIVE: To evaluate the EasyCD4 assay, a less expensive method to enumerate CD4+ lymphocytes, in resource-limited settings. DESIGN: Cross-sectional study conducted in the United States and Uganda. METHODS: We compared CD4+ cell counts obtained on replicate samples from HIV-infected patients by the EasyCD4 assay, a microcapillary flow-based system, and by standard flow cytometry or FACSCount with linear regression and the Bland-Altman method. RESULTS: Two hundred eighteen samples were analyzed (77 in the United States and 141 in Uganda). In the United States, mean +/- SD CD4 was 697 +/- 438 cells/microL by standard flow cytometry and 688 +/- 451 cells/microL by EasyCD4. In Uganda, the mean +/- SD CD4 was 335 +/- 331 cells/microL by FACSCount and 340 +/- 327 cells/microL by EasyCD4. The 2 methods were highly correlated (US cohort, r2 = 0.97, slope = 1.0, intercept = -18; Ugandan cohort, r2 = 0.92; slope = 0.95; intercept = 23). The mean differences in CD4 cell counts were 9.0 and -4.6 cells/microL for the US and Ugandan cohorts, respectively, and they were not significant in either cohort. In the Ugandan cohort, sensitivity and specificity of the EasyCD4 for CD4 below 200 cells/microL were 90% and 98%, respectively. Positive predictive value was 96%; negative predictive value was 93%. CONCLUSIONS: Our results suggest that EasyCD4 may be used with high positive and negative predictive value in resource-limited settings.

CD4 Lymphocyte Count↗