Investigations
1st investigations to order
microscopy and culture (blood, wound, fluid, tissue)
Test
Early diagnosis of streptococcal infections in most patients is made with Gram stain of the infected fascia or muscle, obtained by surgical debridement. This reveals gram-positive cocci in pairs and chains. Growth from blood cultures usually occurs in 8 to 24 hours, and blood cultures are positive in 60% of streptococcal cases.[41]
Bacteraemia with positive blood cultures is rare in staphylococcal TSS.[4][41][88]S aureus is isolated from mucus or wound sites in 80% of patients with staphylococcal disease.[12]
Result
positive for group A streptococcus or Staphylococcus aureus
FBC
Test
Increased WBC count and anaemia and decreased platelet count are sensitive but not specific for the diagnosis of streptococcal or staphylococcal TSS.
Result
leukocytosis with a left shift; anaemia; thrombocytopenia with platelets <100 x 10⁹/L (100 x 10³/microlitre)
coagulation profile
Test
Including prothrombin time, partial thromboplastin time, and fibrinogen.
Result
in staphylococcal disease in conjunction with DIC: prothrombin time/partial thromboplastin time may be prolonged; fibrinogen may be low
serum urea and creatinine
Test
Elevated urea and creatinine, and haemoglobinuria are signs of renal failure. Precedes hypotension in 40% to 50% of patients with streptococcal disease.[44]
Result
elevated
urinalysis
Test
Elevated urea and creatinine, and haemoglobinuria are signs of renal failure. Precedes hypotension in 40% to 50% of patients with streptococcal disease.[44]
Result
haemoglobinuria
LFTs
Test
Shows elevation of bilirubin or transaminases more than twice the normal upper limit.
Result
elevated transaminases and bilirubin
creatine kinase (CK)
Test
Elevated CK suggests necrotising fasciitis or myositis. CK may also be elevated in staphylococcal TSS.
Result
elevated in necrotising fasciitis or myositis and in some staphylococcal diseases
serum calcium
Test
Hypocalcaemia is found on admission and throughout the course of streptococcal disease.
Result
low in streptococcal disease
serum sodium
Test
Hyponatraemia may be present on admission and throughout the course of streptococcal disease.
Result
low in streptococcal disease
serum phosphorus
Test
Hypophosphataemia may be present on admission and throughout the course of streptococcal disease.
Result
low in streptococcal disease
serum albumin
Test
Hypoalbuminaemia is found on admission and throughout the course of streptococcal disease.
Result
low in streptococcal disease
serum lactic acid
Test
Lactic acidosis is seen in sepsis resulting from poor tissue perfusion or diminished oxygenation of blood.
Result
elevated in severe sepsis and septic shock
Investigations to consider
Staphylococcus aureus antibody testing
Test
Diagnosis of staphylococcal TSS is supported by acute and convalescent antibody testing.
Result
presence of S aureus in the absence of an acute-phase antibody
chest x-ray
Test
Consistent with acute respiratory distress syndrome.
Result
diffuse bilateral interstitial and alveolar infiltrates
Emerging tests
serotyping
Test
Diagnosis of TSS with presence of phenotypic and genotypic characteristics: M-protein type, serum opacity factor production, protease production, the presence of streptococcal pyrogenic exotoxin (SPE) genes A, B, and C, and in vitro production of SPEA and SPEB. However, these tests are not routinely available in most hospitals.
Result
evidence of streptococcal exotoxins
Use of this content is subject to our disclaimer