The detection of leukocyte esterase activity in urine with a new reagent strip.

An evaluation of the Ames Leukostix reagent strips for the detection of leukocyte esterase activity in urine was undertaken to determine the interlot precision and between reader reliability, to compare Leukostix and Chemstrip LN results, and to determine if the Ames Leukostix reagent strip provides an alternative to, or supplement for, the microscopic detection of leukocytes. A total of 412 urines were analyzed with the Ames and Bio-Dynamics reagent strips. The sensitivity and specificity of Leukostix results, relative to a quantitative chamber count, were 89.4% and 90.4%, respectively. Chemstrip LN provided essentially the same results with a sensitivity of 88.8% and specificity of 92.4%. The between-reader and between-lot reproducibility was excellent, with 99% of the results agreeing within half a color block of each other. The sensitivity of the sediment count relative to the chamber count was 68.9% and the specificity, 97.7%. Performance of the sediment count in addition to use of the reagent strip provided little additional information. On the basis of these results, the Ames Leukostix reagent strip is considered to be a suitable alternative to sediment microscopic examination for the detection of leukocytes in urine.