Stability of N-terminal pro-brain natriuretic peptide after storage frozen for one year and after multiple freeze-thaw cycles.

small-sized hyaline casts, Ͻ4 in each slide; hyaline with medium or large diameter, cellular, granular, granulo-hematic, waxy casts, none; cystine crystals, none; other crystals, rare (Ͻ10 in each slide). We usually notice a high prevalence of pathologic findings (ϳ70%) in microscopic analysis of urine samples from our patients. Applying the published algorithm, we estimated that only 93 samples (31%) would not require microscopic confirmation, but 205 samples (69%) would need microscopic review. The correlations between the results obtained with the UF-50 and the microscope are showed in Table 1 (Cohen K coefficient; SPSS). The concordance in detecting pathologic samples was good for erythrocytes (K ϭ 0.67) and leukocytes (K ϭ 0.72). The UF-50 revealed remarkable flaws with regard to the analysis of crystals and casts, for which the concordance between the two methods is very low (K ϭ 0.043 and 0.08, respectively). These formed elements must be analyzed by microscopy to define their type and/or size. Flags for casts were produced by the instruments for 7% of samples, probably because of interference by squa-mous epithelial cells or mucous threads and cylindroids, without microscopic detection, and 40% of samples with pathologic casts were not recognized by the UF-50. This represents a serious limitation in a laboratory of nephrology. Moreover, the flow cytometer detects only granular and cellular casts. We also tried to evaluate whether flow cytometry is useful in the analysis of erythrocyte dysmorphism by applying the Kitasato criteria (6, 7). However, this system relies on eryth-rocyte volume and size, and the flow cytometer distinguishes erythrocytes on the basis of cellular diameter but cannot recognize dysmorphic eryth-rocytes with altered shape, such as acanthocytes or codocytes (8). Thus, in our study we observed that of 131 samples with microhematuria by mi-croscopy, 41 (31%) had predominantly dysmorphic erythrocytes according to both methods, whereas 59 (45%) had predominantly normal erythrocytes, but 16 (12%) revealed their dysmorphism only when analyzed by phase-contrast microscopy with a significant presence of altered cell shape (acanthocytes), and 15 (11%) showed their dysmorphism only when analyzed by flow cytom-etry, probably because of the presence of high amounts of yeasts or erythrocytes with different sizes. In conclusion, combining the automated and traditional analyses of urinary formed elements in general laboratories—starting with automated cell counting followed by microscopic analysis, which is more specific in revealing morphologic as-pects—may be a time-sparing policy. In a laboratory of nephrology, however , where samples have a …