In General

Enzymes act within the cells (exception: anti- and procoagulatory enzymes). Increased activities are detected when cell membrane permeability is disturbed and enzymes leak into the extracellular fluid. Increased enzyme activities do not necessarily indicate a decreased organ function. Enzyme profiles localize the injuries (e.g. muscle or liver), sequential activity measurements help judging the time course.

AP - Alkaline Phosphatase

The enzyme is localized in cell membranes of many organs as liver, kidney, intestines, mammary gland and bone;
Interpreation: young animals show increased activities due to sceletal growth, in dogs and horses AP is a sensitive marker of cholestasis. Drug therapy can increase alkaline phosphatase activities in dogs (e.g. corticosteroids, anticonvulsants). Fatty liver disease in cats is characterized by up to ten fold increases of alkaline phosphatase activities with only moderately increased GGT elevations .

c-ALP - steroid induced alkaline Phosphatase

Corticosteroids induce the elevation of a hypoglycosilated form of AP. 95% of dogs with hyperadrenocorticism show marked elevations of steroid induced AP activity.
Indication: suspect hyperadrenocorticism, elevated AP activitiy

ALT - Alaninaminotransferase

Lokalisation: Zytosol von Leber und Muskelzellen;
Nur bei Hund, Katze, Primaten, Kaninchen und Ratten leberspezifisch;
Steigt bereits bei erhöhter Permeabilität der Zellmembranen an, daher kein Indikator für Zellnekrosen. Anstieg binnen 12 Stunden nach Insult; Höhe des Anstiegs korreliert zwar mit der Anzahl der betroffenen Leberzellen, gibt aber keinen Hinweis auf Ätiologie oder Grad einer eventuellen Funktionsstörung!

AST - Aspartataminotransferase

Lokalisation: Zytosol und Mitochondrien von Leber und Muskelzellen.
Bei Katze, Rind und Schwein zur Leberdiagnostik geeignet. Erhöhungen der mitochondrialen Fraktion gilt als Hinweis auf eine Zellnekrose (methodisch beim Tier aber z.Zt. nicht möglich).
Zusammen mit CK- Bestimmung zur Diagnose von Weichteilschädigungen.

GLDH - Glutamatdehydrogenase

Lokalisation: Mitochondrien insbesondere im zentrilobulären Bereich der Leberzellen.
Leberspezifisch bei allen Tierarten, Anstiege bei Zellnekrosen und hypoxischen Zuständen (solitärer Anstieg).

gGT - g-Glutamyltransferase

Lokalisation: in fast allen Organen mit Ausnahme von Muskel; höchste Aktivität in Gallengängen, Nierentubuli, Ausführungsgänge der Milchrüsen (membranständig).
Sehr niedrige Basalaktivitäten bei Katzen und Ratten; Cholestasemarker;
Hohe Aktivitäten bei Neugeborenen nach Colostrumaufnahme. Enzyminduktion durch Glukokortikoide und Antikonvulsiva beim Hund.

CHE - Cholinesterase

Indikation: hgr. Aktivitätsverlust bei Vergiftungen mit Organophosphaten

Amylase

Lokalisation: Pankreas, Speicheldrüsen, Darm und Leber.
Indikation: klinischer Verdacht auf akute Pankreatitis
Steigt rasch an, fällt aber nach kurzer Zeit wieder ab.
Unspezifische Erhöhungen bei Dünndarmerkrankungen, mäßige Erhöhungen bei verminderter glomerulärer Filtrationsrate.

Lipase

Lokalisation: Pankreas, Magen;
Indikation: klinischer Verdacht auf akute Pankreatitis;
Unspezifische ggr.-mgr. Erhöhungen bei Entzündungen des vorderen Dünndarms.

CK - Creatinkinase

Lokalisation: Muskulatur
Indikation: Weichteilschädigung, Differenzierung von ALT und AST Anstiegen.
Sehr sensitiv steigt schon bei ggr. stumpfen Traumata an. Rascher Anstieg, bei sistieren der Noxe Abfall binnen 8 Tagen.
Bestimmung im Liquor: unspezifischer aber empfindlicher Indikator für ZNS-Erkrankungen.
Isoenzymbestimmungen bei Tieren nicht relevant.

LDH - Laktatdehydrogenase

Lokalisation: alle Gewebe, keine Organspezifität. Anstiege bei entzündlichen und degenerativen Prozessen.
Extreme Erhöhungen in Punktaten können Hinweis auf eine bakterielle Infektion sein,
moderate Erhöhungen können einen Hinweis auf ein tumoröses Geschehen geben.

Sodium

most important extracellular cation

• Function: main constituent of extracesllular osmotic presure, regulates water movement between body-compartments.
• Indication: all diseases combined with fluid loss like vomiting, diarrhea, PU/PD, dehydration, seizures.

Potassium

most important intracellular cation 

• Function: regulates intracellular enzymatic reactions, main component of transmembraneous potentials (muscle contraction).
• Indication: fluid loss, vomiting, diarrhea, PU/PD, dehydration, cardiac arrhythmia (bradycardia), anorexia, fluid therapy, myopathy, renal disease, paralytic ileus.

Chloride

Most important extracellular anion, regulates acid-base household and osmolality. Parallel changes of sodium and chloride are consequences of changes in water content. 

• Indication: vomiting, diarrhea, PU/PD, acid-base disturbances

Calcium

• Function: regulates enzymatic reactions, muscelcontraction, nerval activity and cell membrane permeability. The unbound calcium ion is the  biologically active form. Usually the total calcium content is measured, biologically inactive protein-bound and chelated fractions are included – therefore total protein content of plasma or serum is crucial for the interpretation of calcium levels. 
• Indications: PU/PD, lethargy, weakness, hyperexcitability, seizures, cramps, muscle tremors, facial pruritus, fever of unknown origin, tumors (tumor-associated hypercalcemia), renal disease in horses.

Cattle: parturition/lactation-associated hypocalcaemic syndromes.

Inorganic Phosphorus

• Function: constituent of energy rich phosphates in cell metabolism, constituent of bone, renal excretion
• Indication: renal failure (increases simoultaneously with creatinine), disturbances of calcium metabolism, increased values in iuvenile animals (bone-growth).

Cattle: parturition/lactation-associated hypocalcaemic syndromes.

Magnesium

• Function: intracellular cation, mainly in bone and muscle cells
• Indications: refractory hypokalaemia, hypocalcaemia, muscle weakness, ataxy, seizures; critically ill patients develop hypomagnesaemia. 

Cattle: parturition/lactation-associated hypocalcaemic syndromes.

Iron

• Function: constituent of blood and muscle pigment (hemoglobin, myoglobin, oxygen carrier.
• Indication: suspectet iron deficiency anaemia (hypochromic, microcytic anaemia)

Erythrogram

The erythrogram includes the red blood cell count, mean corpuscular volume, hematocrit, hemoglobin concentration and erythrocyte indices. Reduction of red blood cell count and/or hemoglobin contents defines aneamia. Reticulocyte count (immature Erythrocytes) and erythrocyte indices define regenerative and non-regenerative forms of anaemia. Herbivores commonly do not release reticulocytes into the peripheral blood. 
Total protein should be included into the anaemia panel as blood loss anaemia is associated with decreased serum protein.
In complicated cases diagnostic workup should be incited before a blood transfusion is given, as reasonable assessment of anaemia is not possible following a transfusion.

Leucogram

The leucogram consists of total white blood cell count and differential. It is a traditional screening parameter to evaluate general health, stress and disease. Changes in white blood cell counts and differentials vary a lot between species.
For the interpretation of the differential cell count only the absolute numbers are relevant! 
Differentials derived by in house bench-top analyzers must be cross-checked by microscopy!

Platelet Count (PLT)

• Indication: petechia, epistaxis, hematuria without stranguria.

Viability of platelets for electronic counts: 4 hrs.!
Thrombocytopenia: most common laboratory error due to short viability and platelet clumping (especially in cats).

Coagulation profile

For the evaluation of hemostatic disorders beside clinical tests like mucosal bleeding time and platelet counts, global coagulation tests like prothrombin-time, activated partial thromboplastin-time and thrombin-time are determined.

• Indications: hemorrhagic diathesis – rebleeding after initial cessation of bleeding, hematomas after minor trauma, bruises, hemorrhage into joints and body cavities, suspected cumarin toxicosis (prothrombin time rises first as factor VII has the shortest half life), suspected hereditary bleeding disorders (hemophilia A and B activated thromboplastin time increased!), small hemorrhages like petechiae perform a platelet count!

Note: citrate anticoagulated blood is necessary for coagulation profiling – citrated vials (light blue stopper), proper filling of tube is mandatory (1 part sodium citrate + 9 parts whole blood) mix thoroughly!

Bone-marrow Evaluation

Decrease of one or more cell lines in peripheral blood (sequential evaluations) of unknown origin, suspected blood parasites, tumors of the hemolymphatic system and tumor staging are indications for bone marrow evaluation. Simultaneously a CBC should be performed. A detailed case history (medications) is mandatory for interpretation.

FeLV

Test for feline leukaemia virus antigen in Serum, Plasma or whole blood.

Dirofilariosis

Dirofilaria immitis (heart-worm) is a blood parasite of dogs and cats. Endemic areas in warm regions also in Europe – travelling animals!
Specific test for antigen of Dirofilaria immitis in Serum, Plasma or whole blood.

Serum only for hormone determinations! In our system heparin and other anticoagulants might influence the analysis

Cortisol

Cortisol is synthesized by the adrenal glands. It is a stress hormone and biological variance is high. Dysfunctions in both directions might occur. For evaluation of adrenocortical function the following function-tests can be applied:

• ACTH stimulation test (90 min), screening: Hypoadrenocorticism (Addison’s disease), iatrogenic Cushing Syndrome, Hyperadrenocorticism
• Low dose dexamethasone screening test (8 hrs.), validation: Hyperadrenocorticism (Cushing Syndrome)
• High dose dexamethasone suppression test (8 hrs.):
  to differentiate between adrenal and pituary dependent hyperadrenocorticism.
  
• Cortisol/Creatinine ratio in urine is a test to exclude hyperadrenocorticism from the list of differentials.

Thyroxine

Is a hormone secreted by the thyroid gland. Hormone secreting thyreoid adenomas often lead to hyperthyroidism in older cats (palpate ventral neck region!).  Elevated serum thyroxine levels are diagnostic.

• Canine Thyroxine, c-T4
  As the thyroxine-binding protein levels in dogs are low, the total T4 levels are lower than in man. Therefore a test kit adapted to the lower diagnostic range in dogs is applied.
• Canine TSH: c-TSH
  Decreased T4 and elevated c-TSH is diagnostic for primary hypothyroidism in dogs. Combined testing is a substitute for the TSH-stimulation test, which is still considered to be the gold standard.

Digoxin

• Indication: suspected intoxication (cardiac arrhythmia), therapeutic failure, patients with altered metabolism (e.g. renal insufficiency), unknown premedication;

Material: SERUM ONLY

Phenobarbital

Is a drug of first choice in treating idiopathic epilepsy. Absorption is slow after oral application and the plasma level peaks after 4-10 hours.

• Indication: check of application regime, suspected intoxication.

Material: serum or plasma

Theophylline

Is a methylxanthine-derivative with bronchodilatatory function. It is metabolized in the liver;

• Indication: check of application regime. 

Material: SERUM ONLY

Urine status is an essential part of routine health checks. Urinalysis evaluates not only the function of kidneys and urinary tract, but also carabohydrate, bilirubin, hemoglobin and myoglobin metabolism. 
Urinalysis consists of physical, chemical and microscopic parameters.

Serumprotein - Electrophoreses

• Indication: changes in serumproteincontent, e.g. profound hyperproteinaemia without blood volume depletion, suspected immunoglobulindeficiencies; A specific diagnosis is rarely obtained, but absolute and relative changes of proteinfractions mainly albumins and globulins are assessed. 

Specimen collection: only SERUM, simultanous totalprotein determination.

Cytologic evaluation of cells of lumps and bumps, mucosal swabs, secretions and body fluids is a valuable diagnostic tool. 

Proper sampling and sample preparation are mandatory. 

If no specific diagnosis can be achieved at least the next diagnostic step can be specified. 
A minimum of two slides per lesion is suggested!