Chapter 7 Objectives
     At the end of this chapter, the reader should be able to do 
     the following:
        Define the terms clearance, glomerular filtration rate, intrinsic 
         clearance, and extrinsic clearance.
        Correct refractometer readings due to increased glucose and 
         protein concentration. 
        Calculate the analyte concentration per volume of collection of 
         urine analytes.
        Calculate the quantity of analyte collected in urine per unit of time 
         of collection. 
        Calculate and convert the quantity of analyte measured in 
         milligrams per deciliter into grams per day. 
        State the clearance formula.
        Calculate uncorrected creatinine clearance rates.
        Use a nomogram and calculate creatinine clearance rates. 
        Define the estimated creatinine clearance formula.
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                                                                Urine Tests
           Urinalysis is one of the most common 
                laboratory tests performed.
                  Chemically impregnated strips are used to 
                       determine chemical constituents.
                  Microscopic evaluation of sediment helps determine 
                       the cellular constituents.
                  Screening tool for various diseases and conditions, 
                       such as diabetes, UTIs, metabolic disorders, and 
                       liver disorders
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           Corrections Used for the Refractometer
             Calibration
                   Urinalysis measures specific gravity (SG) of the 
                         urine.
                   SG indicates quantity of dissolved solids in urine, 
                         such as urea and chloride.
            Refractometer, or total solids (TS) meter, 
                 measures specific gravity indirectly by the 
                 refractive index of the urine.
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           Corrections Used for the Refractometer 
                                                                       (Cont.) 
          Refractive index
                 Ratio of the velocity of light in air to the velocity of 
                      light in solution
                 Angle at which the light passes through the solution is 
                      mathematically converted into units of SG.
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                                        Corrections Used for the 
                                            Refractometer (Cont.) 
           Only one drop of 
                urine is required with 
                a refractometer.
           Can be calibrated 
                with deionized water 
                to read 1.000 and 
                5.00%(w/v) NaCl to 
                read 1.022
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