Investigations

The diagnosis is usually made on clinical grounds and laboratory tests are rarely needed (1). Full blood count and biochemistry are normal. There is no abnormality revealed on imaging studies of the head and spine.

Three laboratory tests are available which could be used for laboratory conformation (the first two tests) and support the diagnosis (third test) of tetanus:

• tetanus toxin in a serum sample
  • provides laboratory confirmation of a clinical diagnosis of tetanus
  • absence of serum tetanus toxins does not rule out a clinical diagnosis
  • samples must be collected before any immunoglobulin therapy
• isolation of tetanus bacillus from infection site
  • C. tetani is only very rarely recovered from the infection site
• tetanus toxin antibodies in the serum
  • low levels or absent antibody to tetanus toxoid may provide laboratory evidence in support of a clinical diagnosis
  • samples must be collected before any immunoglobulin therapy (1).

Reference:

• (1) Health Protection Agency (HPA) 2011. Tetanus: General Information