We assessed the analytical performance of the Abbott IMxTM immunoassay analyser for total beta human chorionic gonadotropin (Beta hCG), follicle-stimulating hormone (FSH) and luteinising hormone (LH). The within-run CVs for various analyte concentrations were 2% to 6% while those for between-run imprecision in routine assay ranged from 4% to 10%. IMxTM values correlated well with radioimmunoassay for beta hCG, and immunoradiometric assay for FSH and LH; the correlation coefficients (r) were 0.97, 0.99 and 0.98 for total beta hCG, FSH and LH respectively. The average sensitivities were approximately 3.1, 0.2 and 0.5 iu/l for beta hCG, FSH and LH, respectively. Sample carry-over was not detected and there was negligible cross-reaction between LH and beta hCG in the respective assays. The automatic sample dilution protocol for beta hCG was superior to the manual procedure. The IMxTM is easy to operate and is able to process 24 samples in 40-45 minutes.
Eighty-nine patients who had hydatidiform moles evacuated at the General Hospital, Kuala Lumpur, were followed with serum beta hCG determinations from October 1988 to June 1991. A regression curve for serum beta hCG, as measured by RIA, was derived from the results of 47 of the patients who demonstrated spontaneous regression of serum beta hCG titres. All 47 patients had normal serum titres at 135 days after evacuation. The mean time taken to reach normal level was 82.6 days, while the range was 39 to 135 days (5 to 19 weeks).