The setting for dilution was changed to 50 ng/ml as the dilution point for psa at the customer site.The urgent field corrective action cc 16-05.A.Ous and urgent medical device correction cc 16-05.A.Us that were issued in december 2015 indicated that based on siemens' internal testing, samples with total psa concentrations between 4,200 ng/ml (ug/l) and 8,400 ng/ml (ug/l) do not assay >100 ng/ml (ug/l) but instead result in falsely depressed concentrations of approximately 50 ng/ml (ug/l) to 94 ng/ml (ug/l).The cause for the discordant psa result is the high-dose hook effect.The instrument is performing within specifications.No further evaluation of the device is required.The ifu states inthe high-dose hook effect section: "patient samples with high total psa levels can cause a paradoxical decrease in the rlus (high-dose hook effect).In this assay, patient samples with total psa levels as high as 10,000 ng/ml (10,000 ug/l) will assay greater than 100 ng/ml (100 ug/l).The ifu states in the interpretation of results section: "results of this assay should always be interpreted in conjunction with patient's medical history, clinical presentation and other findings." the ifu states in the limitations section: "note: do not interpret levels of psa as absolute evidence of the presence or the absence of malignant disease.Before treatment, patients with confirmed prostate carcinoma frequently have levels of psa within the range observed in healthy individuals.Elevated levels of psa can be observed in patients with nonmalignant diseases.Measurements of psa should always be used in conjunction with other diagnostic procedures, including information from the patient's clinical evaluation.The concentration of total psa in a given specimen determined with assays from different manufacturers can vary due to differences in assay methods, calibration, and reagent specificity.Total psa determined with different manufacturers' assays will vary depending on the method of standardization and antibody specificity.".
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