Biomedical subjects

J Neukammer

Publications and source records attributed to J Neukammer.

10 recordsLinked to original sources

PubMed2001

Relative frequency of malaria pigment-carrying monocytes of nonimmune and semi-immune patients from flow cytometric depolarized side scatter.

BACKGROUND: Recently, it was observed that malaria can be detected by performing automated complete blood count analysis including depolarization measurement of scattered laser light. To explain large discrepancies in sensitivity and specificity observed in semi-immune and nonimmune malaria patients, we determined the relative frequencies of malaria pigment-carrying monocytes (PCM) by flow cytometric measurements combined with rare event analysis. METHODS: An experimental cell-sorting unit utilizing argon, krypton, and helium-neon lasers measured the relative frequencies of leukocytes of malaria patients. Single white blood cells showing high intensity in their depolarized side scatter were sorted for subsequent microscopic analysis. RESULTS: From microscopic inspection of sorted cells, we identified malaria PCM as a distinct cluster in scatter diagrams that is well separated from normal leukocytes. For nonimmune patients, the average relative frequency of PCM is 1.5 x 10(-4) (median), for semi-immune patients 8.8 x 10(-4), and for malaria-negative persons 4.4 x 10(-6). Results derived from depolarized side scatter at 488, 633, or 647 nm agree well. Furthermore, malaria pigment-carrying neutrophilic granulocytes were identified microscopically after sorting. We discuss briefly how pigment-carrying neutrophils might be differentiated from normal leukocytes and PCM by using flow cytometry and measuring depolarized side scatter at two wavelengths. CONCLUSION: Our results confirm the feasibility of malaria detection by flow cytometry for semi-immune patients and extend malaria detection to nonimmune patients with low frequencies of PCM. High sensitivity and specificity for malaria detection were obtained.

Cell Separation↗

PubMed1999

Evaluation of a new reagent for preserving fresh blood samples and its potential usefulness for internal quality controls of multichannel hematology analyzers.

We describe a new, easy-to-use reagent, Cyto-Chex (Streck Laboratories, Omaha, Neb), that preserves fresh whole blood in a non-cross-linking, nonformalin manner. Target values assigned to fresh blood were essentially met after preservation and storage of up to 31 days. Respective mean analytic inaccuracies and short-term intra-assay coefficients of variation (n = 30) were as follows: WBCs, 6.7% and 1.99%; RBCs, 0.7% and 0.76%; hemoglobin, -1.8% and 0.79%; hematocrit, -0.3% and 0.75%; mean corpuscular volume, -1.0% and 0.78%; and platelets, 6.9% and 3.12%. Linearity of dilution-sensitive analytes was satisfactory over a wide range of dilutions after preservation of blood samples. Ten independent laboratories using 10 different instruments determined day-to-day interassay imprecision during four 7-day periods after blood preservation. Mean interassay coefficients of variation for participating laboratories were WBC, 1.92%; RBC, 1.00%; hemoglobin, 1.29%; hematocrit, 2.00%; and platelets 3.29%. Cyto-Chex enables long-term monitoring of instrument accuracy and precision with retained blood specimens of healthy persons. Blood from patient cohorts with various hematologic disorders and with a wide range of numeric abnormalities and/or parameter aberrations can be preserved satisfactorily with this reagent. The reanalysis of preserved patient blood samples is an important adjunct to the use of commercial control material in quality control programs of multichannel hematology analyzers.

Blood Preservation↗

PubMed1998

Flow cytometric differentiation of erythrocytes and leukocytes in dilute whole blood by light scattering.

We have determined differential scattering cross sections of sphered erythrocytes integrated over the solid angle accepted by our detectors at wavelengths varying between 379.5-632.8 nm, employing Ar+-, Kr+-, and HeNe-laser radiation. Integrated differential cross sections for forward and orthogonal light scatter exhibit a pronounced minimum at about lambda = 413 nm, caused by the strong absorption of light by oxyhemoglobin. Experimental data are in good agreement with values calculated by the Mie theory. Simultaneous measurements of forward and orthogonal light scatter using Kr+-laser radiation (lambda = 413.1 nm) allow flow cytometric differentiation of (native) erythrocytes, thrombocytes, and leukocytes as well as subpopulations of leukocytes, i.e., granulocytes, lymphocytes, and monocytes in dilute whole-blood samples. Lysis of red blood cells or staining of white blood cells is not required to obtain absolute leukocyte counts or differential white blood cell counts.

Blood Cells↗

PubMed1991