Laboratory Medicine Updates - June 10, 2002

University of Virginia Health System
Medical Laboratories
“Quality You Expect, Service You Deserve”

  LABORATORY MEDICINE UPDATE
June 10, 2002

 

Inpatient Laboratory Cumulative Reports Discontinued

As a part of cost saving measures within the Health System, the printing of Cumulative Laboratory Reports for patients currently admitted to inpatient locations were discontinued on June 3rd, 2002.   With the availability of Laboratory results in both MIS and CAS, there are multiple ways to access laboratory results.  The continued printing of these laboratory reports merely supplies redundant information.

If the need should arise, Cumulative Laboratory Reports can be generated as requested for individual patients.  Please call 4-5169 to make requests and arrange for report distribution.

Questions concerning this change should be directed to the following individuals:

James C. Boyd, M.D.                                                     
Medical Director, Lab Information Systems
Ph: 924-5198                                                              

Bob Burns
Manager, Lab Information Systems
Ph: 924-2847

Changes in Reference Intervals

Due to changes in reagent formulation or instrumentation, new reference intervals have been established for the following analyses:

Folate:

Serum Folate: >5.38 ng/mL

RBC Folate: 280-791 ng/mL

CMV Serology Screening:

Negative: <0.9

Equivocal:  0.9 - 1.1

Positive:  > 1.1

Rubella Serology Screening:

Negative:  <5 IU/mL

Equivocal:  5.0 - 9.9 IU/mL

Positive:  > 10 IU/mL

Toxoplasma Serology Screening:

Negative:  <6.5 IU/mL

Equivocal:  6.5 - 7.9 IU/mL

Positive:  > 8 IU/mL

Reminder: LAP is now a Send-out Test

As published in the May 6, 2002 issue, LAP testing (Leukocyte Alkaline Phosphatase) is now being performed by our referral laboratory Quest Diagnostics.  Specimen requirement is a Sodium Heparin (Greentop) tube or two (2) well-made smears from a finger stick with no fixative.  Sample should be received in the Core Laboratory no later than 2 PM for analysis that evening due to sample stability.

 

Collection of Samples for Calcitonin Analysis

Samples for calcitonin analysis must be placed on ice immediately after collection and transported to the laboratory on ice due to sample stability.  The preferred specimen type is a red-top tube, although an SST is acceptable.  Minimum volume required is 3 mL whole blood.  Sample should be drawn after an overnight fast.

 

Bio-Available Testosterone now available in-house

Bio-Available Testosterone is now available through the Core Laboratory.  This panel will consist of three results:

Testosterone (ng/dL)

Sex Hormone Binding Globulin (nmole/L)

Free Androgen Index – a calculated ratio of Testosterone/SHBG following conversion of the Testosterone result to nmole/L.

 

Changes in CKMB ordering 

As of May 21, 2002, the CKMB panel (Total CK and MB fraction) can no longer be ordered.  The two components must be ordered separately.

 

New Urinalysis Test Code 

The Core Laboratory is now offering a Urinalysis Only (UAONLY) test.  Urine specimens submitted under this test code will only have the biochemical analysis performed.  If the requesting physician would like abnormal biochemical results followed up with a microscopic examination, the Urinalysis with Microscopic test code UASCR should be used.

 

Calculated Glomerular Filtration Rate (GFR) and New Clinical Action Plan

 

Serum creatinine and creatinine clearance determined from 24-hour collections of urine are notoriously inaccurate estimates of true glomerular filtration rate (GFR) and are affected by age and muscle mass, diurnal variation, various pharmacologic agents that interfere with the assay, menstrual cycle in women, dietary preferences and preparation, degree of renal tubular secretion of creatinine, physical activity, race, and sex. For these reasons a "normal" serum creatinine may have widely different GFR's. Recently Clinical Practice Guidelines (CPG) for chronic kidney disease (CKD)1 were described in a press release of the National Kidney Foundation.  The press release noted that CKD affects 20 million Americans (1 in 9 adults), most of whom are unaware of the problem. More than 20 million others are at increased risk for developing CKD.  Early detection may allow intervention to slow or stop progression of the development of CKD.   According to the guidelines, CKD can be assigned stages and recommended actions according to the patient’s GFR as outlined in the table below.  

 

CHRONIC KIDNEY DISEASE: A Clinical Action Plan

Stage

Description

GFR

(mL/min/1.73m2)

Action

 

At increased risk

>90

(with CKD risk factors)

Screening

CKD risk reduction

1

Kidney damage with normal or ­ GFR

 

>90

Diagnosis and treatment

Treatment of comorbid conditions

Slowing progression

CVD risk reduction

2

Kidney damage with mild decrease in GFR

60-89

Estimating progression

3

Moderate decrease in GFR

30-59

Evaluating and treating complications

4

Severe decrease in GFR

15-29

Preparation for kidney replacement therapy

5

Kidney failure

<15

Replacement (or dialysis)

(if uremia present)

GFR is estimated using the formulae derived from the Modification of Diet and Renal Disease study (MDRD). These formulae have been shown to be the most closely related of any measures to true GFR as measured using radio isotopic and inulin clearance studies2.  Since these formulae do not use urinary creatinine values, 24 h urine collections are not necessary.

Beginning July 2, 2002, the Clinical Laboratories will report estimated GFR on common chemistry panels that include creatinine (Basic Chemistry Panel and Comprehensive Chemistry Panel) using the MDRD calculations3.  The MDRD formula estimates GFR as a function of serum or plasma creatinine and the patient’s age, sex, and race.   The calculation presumes that the patient has stable kidney function without acute change.  The calculated GFR will not be reported for patients <18 yo or >70 yo since the calculation has not been validated in these populations yet.  The calculated GFR is highly correlated with GFR as determined with reference radioisotopic or inulin clearance studies (r = 0.89).   For each estimated GFR, the laboratory report will also supply the CKD stage according to Clinical Practice Guideline table shown above.  If patients are black, the results will have to be multiplied by 1.2, which may stratify the patient into the same or different CKD stage. Information will be presented so the clinician can correct for race and determine staging. This method thus provides the best clinically available estimation of GFR available for use in caring for patients and consideration of an action plan.4

 

The calculated GFR will appear on the laboratory report along with the appropriate stage from the table above and the note “Multiply result by 1.2 if patient is black”. 

 

Example:

 

    CALCULATED GFR      42.5                   mL/min/1.73m2

                        STAGE 3  Multiply result by 1.2 if patient is black

 

REFERENCES

(1)      Clinical Practice Guidelines for Chronic Kidney Disease: evaluation, classification, and stratification. Am J Kidney Dis 39, S1‑S266, 2002.

 

(2)      Levey AS, Bosch J, Lewis JB, Greene TRN, Roth DA. A more accurate method to estimate glomerular filtration rate from serum creatinine: a new prediction equation. Modification of diet in renal disease study group. Ann Intern Med 1999; 130:461‑470. 

(3)      Levey AS, Greene T, Kusek JW, Beck GJ. A simplified equation to predict glomerular filtration rate from serum creatinine. J Am Soc Nephrol 11, 155, 2000.

(4)      Bolton WK, Owen Jr. WF:  Preparing the kidney failure patient for renal replacement therapy.  Postgraduate Medicine. In press, 2002