Analytes Information and Courses from MediaLab, Inc.

Urine reagent strips are normally adequate for urine screening, but occasionally, it may be necessary to perform a secondary procedure to ensure the accuracy of the test result. Confirmatory or secondary procedures are usually performed for one or more of these reasons: To confirm a result that has been obtained on the reagent strip. To obtain a result from a highly pigmented urine that masks the result on the reagent strip. To test for a specific analyte (or analytes) that are not included in the specificity of the reagent strip test. For example, the glucose reagent strip test is specific for glucose, but you want to test for other reducing substances.

External quality control is performed to ensure the reliability of test results between different laboratories. It is also required by CLIA for laboratory accreditation. External quality control is generally accomplished through proficiency testing (PT). In proficiency testing, simulated patient samples are sent out to laboratories for testing. The CLIA standards for handling proficiency testing specimens are as follows: PT samples must be tested with the laboratory's regular patient load. PT samples must be tested the same number of times that patients' samples are tested routinely. Laboratories participating in PT programs must not engage in interlaboratory comparison of PT sample results. Laboratories may not send PT samples to another laboratory for analysis. Laboratories must document all steps of processing for PT samples. PT is required for only the primary method used for testing of analytes in patients' samples during the period covered by the PT event.In return for their participation, the laboratory will receive the following information: results for each analyte sample mean result for each analyte standard deviation of results by the comparative method number of laboratories using the same method standard deviation index (SDI) lower and upper limits of acceptability of resultsPT results that are between the lower and upper limits of acceptability are considered satisfactory. For chemistry, 80% of samples must test within the acceptable range for the PT to be considered successful. External quality control serves several purposes, including: providing a check on internal quality control detecting errors in a lab's methods providing a comparison of testing methods, which is useful in selecting new methods

QC programs require the same sample to be tested every day testing is done. This type of sample is called a control. Controls, which are often purchased from manufacturers, use a human base to ensure the analytes being tested parallel human ranges. Manufacturers pool together many human blood samples to create the large volume needed for a lot number of control.