Evaluation of a rapid method for measuring theophylline in a clinical setting

The need to determine rapidly the theophylline levels of patients in ambulatory settings such as family practice offices has led to the development of instruments purported to be fast, reliable, and cost-effective. This study evaluated one such instrument, the Ames Seralyzer, and compared the findings with those of the Du Pont aca. Forty-six patient samples were split and run on both instruments by trained laboratory personnel. Validation studies yielded a correlation coefficient of r = .9680 (N = 46). Precision assays showed the 27.5 and 82.5 mumol/L (5 and 15 mg/L) levels of theophylline found in control samples produced day-to-day coefficients of variation of 8.8% (n = 43) and 5.8% (n = 35), respectively. After initial evaluation of the Seralyzer, duplicate assays were performed because of erratic results. The evaluators felt that a major source of error was in the diluting and pipetting steps involved in the procedure. The Seralyzer was easy to run but did require some technique-dependent skills.