A case of consistent discrepancies between urine and blood human chorionic gonadotropin measurements.

BACKGROUND: Our laboratory was confronted with two successive urine samples from a single patient which tested positive for human chorionic gonadotropin (hCG) when tested with both qualitative and quantitative assays, combined with no detectable hCG in corresponding plasma samples. METHODS: Serial dilution and recovery experiments were performed in order to investigate the presence of interfering substances or a high-dose hook effect. The ovarian cysts that were removed from this patient were immunohistochemically stained using polyclonal anti-human hCG antibodies. Furthermore, a urine sample was sent to the USA hCG Reference Service for hCG variant analysis. RESULTS: Dilution and recovery experiments in urine and plasma samples were unremarkable. The biopsy stained negative for human hCG and free ß-subunit. hCG isoform analysis in the urine sample revealed that approximately 87.5% of the immunoreactive hCG lacked the ß-subunit C-terminal peptide (CTP). CONCLUSIONS: We report a rare case in which two successive urine samples test positive for hCG whereas in corresponding plasma samples hCG is undetectable. The majority of the total hCG contained a degraded form of ß-subunit that lacks the CTP. This hCG variant, possibly of pituitary origin, is thought to have an extreme fast clearance rate possibly explaining the discordance between the hCG results in urine and plasma samples.

Implementing neonatal screening for haemoglobinopathies in the Netherlands.

BACKGROUND: The birth prevalence of severe haemoglobinopathies such as sickle cell disease (SCD) in the Netherlands has been estimated to be at least 50 newborns per year. Neonatal screening for SCD was added to the Dutch screening programme in January 2007. We here evaluated three high performance liquid chromatography (HPLC) systems for application in neonatal screening for haemoglobinopathies, and present the results of a subsequent pilot screening programme. METHODS: The Variant NewBorn Screening (Vnbs) HPLC system (Bio-Rad) was validated by analysing 131 blood samples and blood mixtures. Subsequently, the performance of the G7 (Tosoh BioScience) and Ultra (Primus Corporation) was compared with the Vnbs. The three HPLC analysers were tested in a pilot screening programme on 21,969 dried blood spot samples from the routine Dutch neonatal screening programme. RESULTS: The pilot screening resulted in 188 abnormal patterns. The three HPLC devices presented comparable within- and between-run precision and detected the abnormal samples similarly. The high throughput, sampling systems, presentation of results, and integration of the chromatograms, however, were different. CONCLUSION: All three analysers detected the same abnormal haemoglobins satisfactorily, but integrated the chromatograms with variable imprecision. Comparison of the results suggested that the Bio-Rad Vnbs was the preferred system. However, software adjustments were required to improve the diagnostic potential of this device for screening for beta- and alpha-thalassaemia.