Multilayered film analysis: evaluation of ammonia and creatinine slides.

We evaluated the Kodak Ektachem multilayer ammonia and creatinine slides. For various concentrations of control material the precision (CV) within- and (between-day) ranged from 0.8 to 7.8% (4.4-9.0%) for ammonia, and 1.9-25.1% (3.6-13.9%) for creatinine. A number of commercial control fluids were unacceptable choices due to the presence of elevated endogenous ammonia levels. For both analytes, analytical recovery was in the range of 100 to 108%. Comparison with the Jaffe reaction demonstrated good correlation for creatinine, and linearity was judged acceptable for both analytes. For ammonia, serum values were nearly double those of paired plasma samples. Plasma and serum samples, therefore, cannot be used interchangeably. No serum versus plasma differences were observed for creatinine.