Evaluation of sporadic bovine alkaline phosphatase interference in the Beckman Access unconjugated estriol (uE3) assay affecting maternal serum screening results.

OBJECTIVES: Bovine alkaline phosphatase (BALP) mediated interference is a potential issue in the Beckman Access unconjugated estriol (uE3) assay. As the uE3 assay is a component of second trimester maternal serum screening characterizing this interference is essential for delivering accurate trisomy 18 and trisomy 21 risks. DESIGN AND METHODS: Residual serum samples (n = 517) were measured by two different lots of uE3 assay. Scavenger BALP (sBALP) was added to all samples to remove potential BALP dependent interference and assessed using both lots of uE3 reagent. RESULTS: BALP mediated interference was observed in similar frequency in both lots of reagent (~3%), although the patterns of positive and negative interference differed between the lots. Pretreatment with sBALP improved lot-to-lot comparison. The presence of BALP related interference was not related to the concentration of endogenous human alkaline phosphatase. The use of polyethylene glycol and sBALP treatment appeared to mitigate BALP mediated interference equally well, and resulted in concordance in measured uE3 concentrations between reagent lots. Additionally, heterophile antibody interference was observed in two samples affected with BALP interference, and the heterophile antibody interference was resolved by both PEG and heterophile antibody blocking reagent treatment, but not sBALP treatment. While the maternal screen numeric risk for affected samples changed, the risk classification changed from a negative to positive screen in two samples. CONCLUSIONS: Interference in the uE3 assay has the potential to affect maternal serum risk calculations in different reagent lots, and pretreatment of samples with scavenger BALP or PEG should be considered in cases of unexplained uE3 concentrations.

Comparing the performance of CA 15-3 CSF to cytology in a cohort of patients with breast cancer leptomeningeal metastasis.

BACKGROUND AND OBJECTIVE: Leptomeningeal metastasis (LM) can occur as a late manifestation of breast cancer and has traditionally been diagnosed by CSF cytology; however, cytology suffers from low sensitivity and it is believed that many cases of LM go undiagnosed. Some studies have suggested the use of CA 15-3 in CSF (CA 15-3 CSF) to aid in the detection of LM. The purpose of this study was to compare the performance of CA 15-3 CSF to cytology for the detection and treatment monitoring of breast cancer LM. METHODS: CA 15-3 CSF requests between 2014 and 2016 were retrospectively reviewed. Fifty-two measurements from nine patients were from our health system and had corresponding CSF cytology measurements. Concordance between CA 15-3 CSF and CSF cytology was calculated. For patients with quantifiable CA 15-3 CSF, sequential determinations of CA 15-3 and cytology were compared over time to assess correlation of CA 15-3 CSF concentration and cytology with disease status. RESULTS: At the time of initial testing, seven of the nine patients (78%) had positive cytology. Two samples (22%) had quantifiable CA 15-3, both of which were also positive by cytology. The positive concordance between all cytology and CA 15-3 measurements was 9% (2/22), while negative concordance was 100% (30/30). Sequential CA 15-3 and cytology measurements showed a decrease in CA 15-3 that paralleled changes observed with cytology. CONCLUSIONS: In this cohort of patients, CA 15-3 CSF performance was neither superior nor complementary to cytology for the detection of LM, nor did the combination of CA 15-3 CSF and cytology improve performance over cytology alone.