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Kathleen Johnson

Publications and source records attributed to Kathleen Johnson.

5 recordsLinked to original sources
PubMed2004

Biomarkers of aging: from primitive organisms to humans.

Leading biologists and clinicians interested in aging convened to discuss biomarkers of aging. The goals were to come to a consensus, construct an agenda for future research, and make appropriate recommendations to policy makers and the public-at-large. While there was not total agreement on all issues, they addressed a number of questions, among them whether biomarkers can be identified and used to measure the physiological age of any individual within a population, given emerging information about aging and new technological advances. The hurdles to establishing informative biomarkers include the biological variation between individuals that makes generalizations difficult; the overlapping of aging and disease processes; uncertainty regarding benign versus pathogenic age-related changes; the point at which a process begins to do damage to the organism, and, if so, when does it occur; and when to distinguish critical damage from noncritical damage. Finally, and significantly, it is difficult to obtain funding for this research.

Aged↗
PubMed2004

Performance characteristics of the Coulter LH 500 hematology analyzer.

The challenge for modern hematology laboratories is to provide accurate and reproducible results, with seamless performance between facilities, in a cost-effective manner. Beckman Coulter recently developed the Coulter LH 500 to meet the needs of smaller laboratories or serve as a backup in larger laboratories. The principal goal of this study was to validate all parameters and performance specifications of the LH 500 compared to the Coulter LH 750 predicate analyzer. A total of 245 spent clinical samples from the London Health Sciences Centre (LHSC) and 251 from the University of Pittsburgh Medical Center Health System (UPMCHS) were analyzed during the study. The samples were selected to include 75% abnormal and 25% normal blood samples. According to the results of a rank sum test, there was no significant difference between the LH 500 and LH 750 for all complete blood count parameters (P > .05) except the red cell distribution width, which showed a slight negative bias on the LH 500. Differential parameters comparing the LH 500 to a 400-cell manual differential showed correlation coefficients (r2) from 0.75 to 0.99 for all parameters except basophils. Of the samples run on the LH 500 at LHSC, the false-positive differential flagging rate was 17.32% and the false-negative rate was 3.03%. Sensitivity was 82.93%, specificity 78.95%, and efficiency 79.65%. At UPMCHS, the false-positive differential flagging rate was 13.37% and false-negative rate 2.97%. Sensitivity was 91.89%, specificity 78.91%, and efficiency 83.66%. Overall, the LH 500 performed accurately and reproducibly compared to the LH 750 and the reference procedures. It would be an excellent second instrument for larger laboratories concerned with harmonization of instrumentation and reagents or as a primary instrument for smaller hematology laboratories with limited space.

Blood Cell Count↗
PubMed2003

Validation of body fluid analysis on the Coulter LH 750.

The role of the hematology laboratory in the analysis of body fluid has been to provide accurate enumeration of red blood cells (RBCs), total nucleated cells (TNCs), and differentials by manual analysis. Three hospitals (London Health Sciences Centre, University of Pittsburgh Medical Center, and University of Michigan Health System) participated in the assessment of the performance of automated analysis of body fluid by the Beckman Coulter LH 750, an impedance-based hematology analyzer. We evaluated the accuracy of analysis results for both the TNCs and RBCs of 372 samples (158 serous fluid, 148 cerebrospinal fluid [CSF], 66 synovial fluid) run on the LH 750 compared to results obtained from manual chamber counting. Of the 372 samples, 152 were suitable for evaluation of accuracy of the automated TNC. The remaining 220 samples were either flagged for interfering substances or the reference results were < 0.2 x 10(9)/L, below the background limit of the analyzer. Correlation coefficients for serous fluid were 0.895, P = .88; for CSF, 0.993, P = .84; and for synovial fluid, 0.836, P = .94. Of the 372 samples, 106 had RBC counts greater than 0.01 x 10(12)/L and were used for method comparison. Correlation coefficients for serous fluid were 0.957, P = .66; for CSF, 0.849, P = .55; and for synovial fluid, 0.667, P = .81. Linearity and precision studies showed excellent agreement for both TNC and RBC parameters. Low-level sensitivity excluded the majority of cerebrospinal (119) and a small number of peritoneal dialysate fluid samples (8), which require accurate enumeration at clinical decision points between 0 to 100 cells/microliter. In the case of synovial and serous fluids, however, most clinicians are interested in TNC counts above 0.2 x 10(9)/L, and RBC counts are relevant only if they are significantly increased (> or = 0.05 x 10(12)/L). Adopting the criteria of reporting TNC counts as < 0.2 x 10(9)/L or accurate enumeration on counts > or = 0.2 x 10(9)/L, clinically relevant results could be provided by automated analysis in 93.8% of serous fluids and 85.8% of synovial fluids.

Blood Cells↗