Calcium, Ionized, Serum
Method Description Describes how the test is performed and provides a method-specific reference
Ionized calcium is measured using an ion-selective electrode on NOVA Stat Profile Critical Care Xpress (CCX). The sensor requires a sensing (ion-selective) membrane, a reference electrode, and an internal filling solution. Internal filling solution provides a fixed concentration of the ion and the sample provides a second ion concentration. A suitable electrode membrane is selectively permeable to the ionized calcium in the sample. This selective permeability establishes an electrical potential as the charge associated with the ion leaves its counter-ion behind in solution. The magnitude of this electrical potential is determined by the concentration difference between the two sides of the membrane.
pH is measured using a hydrogen ion-selective glass membrane. One side of the glass is in contact with a solution of constant pH. The other side is in contact with a solution of unknown pH. A change in potential develops, which is proportional to the pH difference of these solutions. This change in potential is measured against a reference electrode of constant potential. The magnitude of the potential difference is a measure of the pH of the unknown solution.
Ionized calcium and pH are measured concurrently and the ionized calcium value is calculated at a standard pH of 7.40. (Instructional Manual: NOVA Stat Profile Critical Care Xpress [CCX] Nova Biomedical, Waltham, MA, November 2007)
Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
Monday through Friday, Sunday; Available STAT
Analytic Time Defines the amount of time it takes the laboratory to setup and perform the test. This is defined in number of days. The shortest interval of time expressed is "same day/1 day," which means the results may be available the same day that the sample is received in the testing laboratory. One day means results are available 1 day after the sample is received in the laboratory.
Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result
Specimen Retention Time Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location The location of the laboratory that performs the test