Analytic inaccuracy resulting from hematology specimen characteristics. Three cases of clinically misleading artifacts affecting white blood cell and platelet counts.

Sporadically, hematology analyzers generate grossly erroneous results for one or several parameters of the complete blood count (CBC) because of a characteristic or peculiarity of an individual patient specimen. This article presents three cases of relatively less well-known analytic errors of this sort, falsely elevating white blood cell count and platelet count and decreasing total white blood cell count, as determined on a Coulter Aperture Impedence Analyzer. The type of alteration in the CBC parameters and the instrument histogram abnormalities seen in each of these different types of analytic inaccuracy are discussed.

Bacillaemia in leprosy: correlation with slit-skin and nasal smears.

Twenty five multibacillary patients (BL/LL) were studied for bacillaemia. Majority (76%) showed acid fast bacilli in peripheral blood. There was good correlation between bacillary load in peripheral blood and bacteriological index (BI) but poor correlation with morphological index (MI) of skin slit smear and BI/MI of nasal smear.

The "diff-if". Use of microcomputer analysis to triage blood specimens for microscopic examination.

Increasingly, all automated blood counts are not accompanied by a microscopic white blood cell differential. A popular strategy is to obtain a manual differential if any part of the automated blood count and differential is outside specified limits (the "diff-if" strategy). The authors compared two sets of criteria to triage blood counts for manual differentials: previously recommended numeric values, and the analysis of a microcomputer program. In a population of subjects with a high percentage of hematologic disorders, the microcomputer program and the numeric criteria were equally specific (excluding normal blood smears); the program was more sensitive for bands, immature granulocytes, monocytes, nucleated red blood cells, reticulocytosis, teardrops, red blood cell fragments, and hypersegmented neutrophils. The numeric criteria were more sensitive for eosinophilia (less than 1.0 X 10(9)/L) and mandated fewer manual differentials. In a population of predominantly normal subjects, the program was more sensitive for increased bands and equally sensitive for eosinophilia, the only abnormalities observed on the smear. In a population of subjects with predominantly abnormal blood counts, but excluding most primary hematologic disorders, there were few blood smears with abnormalities beyond eosinophilia or increased bands. In both of these groups, the computer program mandated more manual differentials than did the numeric criteria. The authors conclude that microcomputer analysis by the program tested was more sensitive than numeric criteria to identify specimens with abnormal blood smears. Specificity depended on the patient population. The choice of a triage strategy should be based on the individual laboratory's patient population.

Mechanisms of thrombin-induced lung vascular injury and edema.

We have examined the mechanisms of lung vascular injury and pulmonary edema secondary to intravascular coagulation. Alpha-thrombin was infused intravenously to induce pulmonary intravascular coagulation. The results indicate that fibrin and neutrophils are essential requirements for lung vascular injury and pulmonary edema formation. The findings point to a fibrin-neutrophil interaction in inducing neutrophil adherence. Thrombin also has direct effects on endothelial permeability and can contribute to neutrophil sequestration in the lung by increasing endothelial adhesivity. Complement activation can explain only a part of the response. Lipid-derived mediators (e.g., LTB4 and mono HETEs) may be particularly important in the pathophysiology of lung vascular injury and pulmonary edema.