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1330 Creatinine Cross-Matching

Creatinine
VetBooks.ir Definition Specimen Collection and Handling

in most renal/urinary disorders; isosthenuria
Creatinine is a waste product from degradation creatinine concentrations increase in parallel Serum (red top tube) or heparinized plasma
of muscle creatine. and parallel increase in BUN support renal (green top tube)
azotemia. Check medication history and pos-
Physiology sible sources of artifact if creatinine increased Relative Cost: $$ (part of full panel); $
Creatinine is continuously produced from but BUN normal. (single test)
degradation of muscle phosphocreatine and
creatine, and is excreted in urine. It is freely Causes of Abnormally Low Levels Pearls
filtered by glomeruli and is not resorbed by • Thin body condition/muscle The creatinine reference interval is wide, though
renal tubular cells. • Increased glomerular filtration rate values for an individual healthy patient are
• Artifact (e.g., severe icterus) maintained tightly. Therefore, trend of increase
Reference Interval in a single patient’s creatinine is clinically
Dogs 0.6-1.5 mg/dL (53-133 µmol/L); cats: Next Diagnostic Steps to Consider important even when total remains within
0.6-2.0 mg/dL (53-177 mcmol/L) if Levels are Low reference interval.
Evaluate for muscle loss/pathologic weight loss.
Causes of Abnormally High Levels Exclude normal variation (e.g., young animals) AUTHOR: Mary Leissinger, DVM, MS, DACVP
• Decreased glomerular filtration rate (prerenal, or artifact. EDITOR: Lois Roth-Johnson, DVM, PhD, DACVP
renal, or postrenal)
• Animals with greater muscle mass (e.g., Drug Effects
greyhounds) or recent high-protein meal Cephalosporins, vitamin C may cause spurious
(e.g., cooked meat) may have mild increase. increase.
• Artifact (e.g., vitamin C)
Lab Artifacts
Next Diagnostic Steps to Consider Severe icterus may artifactually lower values.
if Levels are High High levels of certain chromogens (e.g., glucose,
Check serum urea (BUN) concentration and ketones, vitamin C) may artifactually increase
urine specific gravity concurrently. Urea and values.

Cross-Matching

Definition Causes of Abnormally High Levels Specimen Collection and Handling
Laboratory procedure to detect antibodies Agglutination (either macroscopic or micro- Two tubes are preferred, one EDTA (lavender
between a patient and a potential blood donor. scopic) or significant hemolysis in the cross- top tube) and one tube without anticoagulant
The major cross-match involves patient’s serum match tubes but not in control indicates an (red top tube or serum separator tube).
and donor blood cells; the minor cross-match incompatible donor.
uses donor serum and the patient’s blood Relative Cost: $$
cells. Important Interspecies Differences
Cats have naturally occurring antibodies, and Pearls
Physiology cross-matching should always be performed • A compatible cross-match does not indicate
Major cross-match determines if there are before transfusion, regardless of previous that the animal and the donor have the same
agglutinating and/or hemolytic antibodies in transfusion history. Transfusion of type A blood blood type; it merely means that erythrocyte
a potential blood recipient that would react into type B cats causes hemolysis (in minutes antibodies were not detected. Therefore blood
with antigens on donor blood cells. Antibodies to 2 days) and severe anaphylaxis. typing remains essential in all donors and
may be naturally occurring (all cats) or induced recipients.
by a previous mismatched transfusion (any Drug Effects • Cross-match should be performed before all
species). Incompatible transfusion can lead to Glucocorticoids and other immunosuppressants repeat transfusions performed more than a
adverse outcome, though incompatible minor may mask incompatibility. few days apart, regardless of blood type or
cross-match is seldom associated with severe results of prior cross-match.
transfusion reactions. Lab Artifacts • This test does not identify antibodies against
Agglutination in the control tubes (patient WBCs, platelets, or plasma proteins.
Reference Interval serum added to patient red blood cells [RBCs] • Cross-match can be performed in clinic
Lack of agglutination or hemolysis indicates or donor serum added to donor RBCs) (p. 1084)
recipient-donor compatibility. indicates reagent contamination or autoag-
glutination. AUTHOR: Deborah G. Davis, DVM, DACVP
EDITOR: Lois Roth-Johnson, DVM, PhD, DACVP

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