Table 1: Adult and paediatric limits of laboratory results which, after confirmation through repeat measurement in the same sample, need urgent notification of the physician 

Parameter

Value

Note

Activated partial thromboplastin time (APTT)

75 sec

Deficiency or inactivity of factor VIII, IX, XI, or XII, with risk of haemorrhage. In persons receiving heparin therapy there is a risk of haemorrhage if the APTT is more than 2.5 times higher than the upper reference limit.

Aminotrans-ferases

> 1000 U/l

Notification depends on the patient population of the clinic or practice in question.

Ammonia

> 100 mg/dl (59 mmol/l)

Risk of hepatic encephalopathy. Comatose states do not usually occur unless levels exceed 300 mg/dl (176 mmol/l).

Anion gap

> 20 mmol/l

Indicative of ketoacidosis or lactacidosis, uraemia, alcohol consumption, salicylate intoxication, poisoning from methanol or ethylene glycol.

Inorganic phosphate

< 1.0 mg/dl (0.32mmol/l) 

> 9.0 mg/dl (2.9 mmol/l)

Muscle weakness, muscle pain, central-nervous symptoms such as disorienta­tion, confusion, convulsions, coma, respiratory insufficiency with metabolic acidosis.

Occurs in acute tumour lysis syndrome and in terminal renal failure.

Antithrombin (AT)

< 50%

There is substantial inhibitor deficiency, which in those with elevated procoagulant activity poses a high risk of thromboembolic complications.

Ethanol

> 3.5 g/l (76 mmol/l)

> 3.5 %

Blood alcohol concentrations of 3-4 g/l can be fatal, even in those who are not simultaneously using medicinal products.

Bilirubin

> 15 mg/dl (257 mmol/l)

Hepatobiliary disease caused mainly by hepatotropic viruses and thus of infec­tious origin with risk of contagion.

Calcium, total

Calcium, free

Calcium, total

Calcium, free

< 6.6 mg/dl (1.65mmol/l)

< 3.1 mg/dl (0.78mmol/l)

> 14 mg/dl (3.5 mmol/l)

> 6.3 mg/dl (1.6 mmol/l)

The ionized calcium concentration is in a range that can lead to hypocalcaemic tetany.

Risk of hypercalcaemic crisis, which is associated with symptoms such as volume depletion, metabolic encephalopathy, and gastrointestinal problems.

Chloride

<  75 mmol/l

>125 mmol/l

Indicative of considerable metabolic alkalosis.

Indicative of massive primary metabolic acidosis or pseudohyperchloraemia in the case of bromide intoxication.

Creatinine

> 7.4 mg/dl (654 mmol/l)

Acute renal failure, e.g. in multiple organ failure or sepsis.

Creatine kinase

> 1000 U/l

Notification depends on the patient population of the clinic or practice in question.

D-dimers

Positive

In disseminated intravascular coagulation (DIC), detection of D-dimers is indica­tive of phase II (decompensated activation of the haemostasis system) or phase III (full-blown DIC).

Digoxin

Digitoxin

> 2.0 mg/l (2.56 nmol/l)

> 40 mg/l (52 nmol/l)

Non-cardiac symptoms such as tiredness, muscle weakness, nausea, vomiting, lethargy, and headache and cardiac symptoms such as sinus arrhythmia, brady­cardia, and various degrees of AV block.

Fibrinogen

< 0.8 g/l

Risk of haemorrhage.

Fibrin monomers

Positive

Indicative of consumption coagulopathy in disseminated intravascular coagula­tion, sepsis, shock, multiple injury, acute pancreatitis, and obstetric complica­tions.

Glucose

< 45 mg/dl (2.5 mmol/l)

 > 500mg/dl

(27.8 mmol/l)

Neuroglycopenic symptoms, which can range from impairment of cognitive func­tions to loss of consciousness.

Diabetic coma due to insulin deficiency. Development of osmotic diuresis with severe exsiccosis and diabetic ketoacidosis (b-hydroxybutyrate > 5 mmol/l, standard bicarbonate < 10 mmol/l).

Haematocrit

< 18% (L/L)

> 61% (L/L)

Corresponds to an Hb concentration of < 6 g/dl. The supply of oxygen to the myocardium is inadequate.

Leads to severe hyperviscosity of the blood, the circulatory resistance is high, there is a threat of heart failure.

Haemoglobin

< 6.6 g/dl

> 19.9 g/dl

Supply of oxygen to the myocardium inadequate.

Corresponds to haematocrit of 61% and leads to hyperviscosity syndrome.

Lactate

> 45 mg/dl (5.0 mmol/l)

Indicator of type A hyperlactataemia, which is caused by an inadequate supply of oxygen to the tissue. Pyruvate is no longer metabolised oxidatively, but reduc­tively.

Lactate dehydro­genase

> 1000 U/l

Notification depends on the patient population of the clinic or practice in question.

Leukocyte count

< 2000/ml

> 50,000/ml

High risk of infection if the granulocyte count is < 500/ml.

Indicative of leukemoid reaction, e.g. in sepsis, or of leukemia.

Lipase

> 700 U/l

Indicative of acute pancreatitis.

Magnesium

< 1.0 mg/dl (0.41 mmol/l)

> 4.9 mg/dl (5.0 mmol/l)

Characteristic symptoms are paresthesias, cramp, irritability, and athetoid tetany. The patient often shows cardiac arrhythmia in conjunction with hypokalemia; arrhythmia is intensified by digitalis.

Reduction of neuromuscular impulse transmission, resulting in sedation, hypo­ventilation with respiratory acidosis, muscle weakness, and reduced tendon reflexes.

Myoglobin

> 110 mg/l

Myocardial infarction should be suspected in patients with angina pectoris.

Sodium

< 120 mmol/l

> 160 mmol/l

Severe disturbance of tonicity (distribution of water between the intracellular and extracellular space) caused by a disturbance of the ADH-thirst mechanism, water absorption, or the renal concentration and dilution capacity. The clinical symp­toms of severe hyponatraemia are the result of volume depletion.

The principal manifestations of severe hypernatremia are disturbances of the central nervous system such as disorientation and increased neuromuscular excitability with twitching and seizures.

Osmolality

< 240 mOsm/kg H₂O

 > 330 mOsm/kg H₂O

Cellular oedema with an increase in cell volume and development of neurological-psychiatric symptoms.

Cellular water loss and intracellular increase in osmotically active substances, which do not permeate the cell membrane. Result: central symptoms and coma.

Osmolar gap

> 10 mOsm/kg H₂O

Indicative of intoxication from non-electrolytes, which increase plasma osmolality, such as ethanol, methanol, ethylene glycol, isopropanol, and dichloromethane.

pCO₂

< 19 mm Hg (2.5 kPa)

> 67 mm Hg (8.9 kPa)

Hyperventilation

Hypoventilation

pH

< 7.2

> 7.6

Such pH values are characteristic of severely decompensated acidosis or alkalosis. Values < 7.20 and > 7.60 are life-threatening.

pO₂

< 43 mm Hg (5.7 kPa)

Such values correspond to a haemoglobin oxygen saturation of less than 80% and are to be regarded as life-threatening.

Potassium

<  2.8 mmol/l

 >  6.2 mmol/l

The main clinical symptoms are neuromuscular, with general weakness of the skeletal musculature. There can be complete paralysis, which can also include the respiratory muscles. ECG: flattening or inversion of the T wave, elevation of the U wave, and ST segment depression. A rapid drop in potassium can lead to cardiac arrest.

Clinical consequences: disturbances of cardiac rhythm. In the precordial leads of the ECG one sees pointed T waves, a lengthening of the PR interval or complete bundle-branch block and atrial asystole. Ascending weakness of the skeletal muscles can lead to flaccid tetraplegia and paralysis of the respiratory muscles.

T4, free

T3, total

> 35 ng/l (45 pmol/l)

> 30 mg/l (46 nmol/l)

Indicative of thyrotoxicosis, a condition detectable clinically and in laboratory tests; the tissues are exposed to too high a thyroid hormone concentration and react to this. Possible causes are: Graves� disease, trophoblastic tumour, hyper­functional adenoma, toxic nodular goitre, and, in rare instances, overproduction of TSH.

Thromboplastin time (TT)

> 27 sec (approx. 50%)

Decrease in the vitamin K-dependent factors II, VII, and X or in factor V. Since all these factors are synthesized in the liver, a decrease in the TT to values below the specified level indicates a considerable disturbance of synthesis. In persons receiving coumarin therapy, there is a risk of haemorrhage if the TT is < 15% � which corresponds roughly to an INR of > 4.

Platelet count

< 20,000/ml

> 1 million/ml

Risk of haemorrhage. Exclude EDTA-induced thrombocytopenia.

Risk of thrombosis.

Troponin

> 0.1 mg/l

Indicative of myocardial infarct or unstable angina pectoris.

Uric acid

> 13 mg/dl (773 mmol/l)

Acute urate nephropathy with tubular blockade and renal failure. The uric acid/creatinine ratio in spontaneous urine in such cases is > 1.0 (mg/mg).

Urea

BUN

> 214 mg/dl (35.6 mmol/l)

> 100 mg/dl (35.6 mmol/l)

Indicative of acute renal failure; unlike pre-renal and post-renal kidney failure, no disproportionate increase in urea compared to creatinine in serum.

Table 2: Critical limits of qualitative laboratory results which must be reported to the treating physician immediately

Cerebrospinal fluid

�           Increased cell count

�           Leukocytosis, tumour cells

�           Glucose lower than in serum

�           Lactate > 20 mg/dl (2.2 mmol/l)

�           Detection of pathogens in Gram stain or agglutination test

�           Strongly positive test strip reaction for glucose and acetone

�           Red cell casts or > 50% dysmorphic erythrocytes

�           Severe haemoglobinuria (no erythrocytes on microscopic examination)

�           Detection of drugs

�           Leukemoid reaction

�           Suspected leukemia

�           Suspected aplastic crisis

�           Sickle cells

�           Malarial parasites

�           Detection of pathogens in Gram staining of blood culture or of exudates and transudates of body cavities

�           Antigenic detection of pathogens with rapid tests such as latex agglutination, immunofluorescence, or immunoassay, e.g. group B streptococci, legionella, Pneumocystis carinii, Cryptococcus, hepatitis B

�           Detection of acid-fast bacilli or detection of M. tuberculosis after amplification (PCR)

�           Cultural detection of salmonellae, shigella, Campylobacter, C. difficile, C. perfringens, N. gonorrhoeae, B. pertussis, N. menin­gitidis, C. diphtheriae, and pathogenic fungi such as Aspergillus, Blastomyces, Coccidioides, Histoplasma, and Cryptococcus

�           Detection of HIV antibodies