Determination of Tear Lipid Film Thickness Based on a Reflected Placido Disk Tear Film Analyzer

This study aims at determining the thickness of the tear lipid layer (LL) observed from a placido-disc-based tear film analyzer. We prospectively collected reflections of placido-disk LL images using a tear film analyzer (Keratograph® 5M, Oculus) from subjects with dry eye symptoms. The LL thickness (LLT) over the inferior half of the cornea was estimated with the use of interference color analysis and the preprocessing of images with and without ring segmentation were obtained and analyzed. Moreover, LLTs before and after 1 h of applying topical ointment (Duratears, Alcon) were compared to validate the estimation of LLT. Our results suggested that the tear LLT can be assessed using a placido-disk-based tear film analyzer and interference color analysis. We verified a high correlation between non-segmented and segmented LL images and estimated LLT increase after applying ointment. In addition, we concluded that LLT can be evaluated by direct interference analysis without segmentation preprocessing.

Characterization of sulfasalazine's interference in the measurement of conjugated bilirubin by the Ektachem slide method.

We describe the cases of four patients who were taking sulfasalazine for inflammatory bowel disease, whose conjugated bilirubin concentrations in serum exceeded their corresponding total bilirubin concentrations as measured with a multilayer film analyzer, the Ektachem 400. Sulfasalazine added to pooled human serum at therapeutic concentrations increased the apparent conjugated bilirubin, as measured with the Ektachem, in a linear and dose-related fashion. Measured unconjugated bilirubin was simultaneously decreased to values less than -3 mg/L. The same interference occurred on the Ektachem 700, but an algorithm prevented the instrument from reporting the results. The major metabolites of sulfasalazine in blood did not interfere with analysis for those fractions of bilirubin. Sulfasalazine's strong absorbance at 400 nm explains its interference with determination of conjugated bilirubin in this instrument.

Age- and sex-specific pediatric reference intervals for biochemistry analytes as measured with the Ektachem-700 analyzer.

Using the Ektachem-700 multilayer film analyzer, we defined age- and sex-specific reference intervals for 20 analytes in sera from a healthy population of neonates and children ages one to 19 years. Upper and lower normal reference intervals for each analyte were determined by nonparametric methods as the 0.975 and 0.025 fractiles, respectively. Newborns have lower concentrations of total protein and albumin, and higher concentrations of phosphate, bilirubin, and enzymes in serum than older children do. Concentrations of urea, glucose, calcium, phosphate, and bilirubin change rapidly postnatally. Outside the neonatal period, no significant age- or sex-related difference was found for plasma glucose, serum amylase, conjugated or unconjugated bilirubin, or lipase. There was no sex-related difference in reference intervals for albumin, total protein, calcium, phosphate, or urea. However, concentrations of uric acid and creatine kinase are much higher in postpubertal boys than in girls. Alkaline phosphatase values peak later in boys. Except for lactate dehydrogenase and gamma-glutamyltransferase, the reference intervals defined here do not differ strikingly from data derived with use of other analyzers. The age- and sex-related trends are independent of method. However, each laboratory should determine the degree to which these reference ranges can be directly applied to analyses performed with another analyzer.

The multilayered film analyzer: glucose in serum, plasma, cerebrospinal fluid, and urine; and urea nitrogen in serum and plasma.

Some basic laboratory performance criteria were studied for the Eastman Kodak glucose and urea nitrogen analyzer. Serum, plasma, urine, and cerebrospinal fluid were tested. Precision, both "within-day" and "between-day," for both analytes was less than 2.2% (CV). Both analytes demonstrated linearity, with about 100% recovery of added substrates. Comparisons with continuous-flow procedures demonstrated good correlation. A variety of sera and plasmas can be used for glucose analysis; oxalate--fluoride-treated plasma is unacceptable for use in analysis for urea nitrogen. We saw no effects on glucose or urea nitrogen analysis from hemolysis, lipemia, icterus, some common drugs, ammonia, or abnormally high protein concentrations. Minimum amounts detectable were: glucose (serum) 104 mg/L; glucose (cerebrospinal fluid) 100 mg/L; and urea nitrogen (serum) 21 mg/L. Calibration procedures are discussed for protein-based and aqueous samples.