Blood Poisoning (Sepsis): Test and Diagnosis

Laboratory parameters of 1st order – obligatory laboratory tests.

  • Small blood count [platelets (thrombocytes) ↓]
  • Inflammatory parameter – PCT (procalcitonin)/Guidelines recommend determination of PCT [procalcitonin increases within a few hours (2-3 h) and reaches its maximum after only 24 hours; PCT concentrations:
    • <0.5 ng/mL exclude severe sepsis or septic shock with high probability
    • > 2 ng/mL make severe sepsis or septic shock highly probable]

    Note: CRP testing in neonates with suspected late-onset sepsis (> 72 hours; late-onset sepsis) does not contribute to either inclusion or exclusion of the diagnosis; sensitivity (percentage of ill patients in whom the disease is detected by use of the procedure, i.e., a positive finding occurs) is 74% with a specificity (probability that actually healthy individuals who do not have the disease in question are also detected as healthy by the test) of 62%.

  • Urine status (rapid test for: pH, leukocytes, nitrite, protein, glucose, ketone, urobilinogen, bilirubin, blood), sediment, if necessary urine culture (pathogen detection and resistogram, that is, testing suitable antibiotics for sensitivity / resistance).
  • Electrolytescalcium, chloride, potassium, magnesium, sodium, phosphate.
  • Fasting glucose (fasting blood glucose), if necessary oral glucose tolerance test (oGTT).
  • Blood gas analysis (BGA) including for the determination of: PaO2/FiO2 (mmHg) [arterial oxygen partial pressure in mmHg/inspiratory O2 concentration; indicates the percentage of oxygen].
  • Thyroid parameters – TSH
  • Pancreatic parameters – amylase, elastase (in serum and stool), lipase.
  • Liver parameters – alanine aminotransferase (ALT, GPT), aspartate aminotransferase (AST, GOT), glutamate dehydrogenase (GLDH) and gamma-glutamyl transferase (gamma-GT, GGT), alkaline phosphatase, bilirubin [↑]
  • Renal parameters – urea, creatinine [↑], cystatin C or creatinine clearance, if necessary.
  • Coagulation parameters – PTT, Quick, antithrombin activity (AT III).
  • Lactate – if lactic acidosis (form of metabolic acidosis in which a decrease in blood pH is due to accumulation of acidic lactate) is suspected [plasma lactate level ≥ 2.0 mmol/l and a pH of < 7.35]Note: Hypoperfusion (decrease in blood flow (perfusion) within a vessel or segment of a vessel) of the tissue is associated with increased lactate levels.
  • Microbiological smears and/or cultures (aerobic and anaerobic blood cultures; 2 times 2 or better 3 times 2 blood cultures) prior to initiation of treatment (i.e., prior to empiric antibiotic/antibiotic therapy); also from venous access or from drains (drainage of body fluids)Note:
    • In preantimicrobial blood cultures (before antibiotic therapy), at least one microbial pathogen was found in 102 of 325 (31.4%) patients; in postantimicrobial blood cultures (after antibiotic therapy), this was still the case in only 63 of 325 patients (19.4%); absolute difference in the proportion of positive blood cultures between pre- and postantimicrobial blood cultures was 12 percentage points, which was significant with a 95% confidence interval of 5.4 to 18.6 percentage points.
    • In urosepsis (acute infection with bacteria from the genitourinary tract), for example, blood cultures are positive in just under 30% of cases.
  • Blood gas analysis (BGA), among others, to determine: PaO2/FiO2 (mmHg) [arterial oxygen partial pressure in mmHg/inspiratory O2 concentration; indicates the percentage of oxygen].

Laboratory parameters of the 2nd order – depending on the results of the history, physical examination and the obligatory laboratory parameters – for differential diagnostic clarification

  • Interleukin-6 (IL-6), tumor necrosis factor (synonyms: TNF α, cachectin, lymphotoxin), or lipopolysaccharide-binding protein-laboratory parameters that may indicate sepsis at an early stage.
  • Toxicological tests – if intoxications are suspected.

Note: Laboratory parameters marked in bold, which are taken into account in the SOFA score (see below classification). In up to 30% of the diseases can not be a confirmed pathogen detection in sepsis.