Diagnosis of Diphtheria
Diphtheria can be diagnosed usually by proper clinical examination, throat culture from the infected area and blood tests:
- Physical examination may reveal the characteristic gray membrane (pseudomembrane) in the throat, enlarged lymph glands and swelling of the neck or larynx.
- Presumptive rapid diagnosis in which methylene blue and Gram stain or immunofluorescent staining is done on the throat cultures to detect the bacteria.
- Definitive identification and diagnosis: a sample of the pseudomembrane is taken and allowed to grow on Loeffler or tellurite selective media, and metachromic granules can be observed with Loeffler stain.
- Toxin A subunit production can be demonstrated in vitro by Elek plate test, polymerase chain reaction probes and in vivo by guinea pig inoculation test.
- In case of blood count there is moderate leukocytosis and possible thrombocytopenia.
- Cardiac enzyme, serum aspartate transaminase (AST) helps to detect myocarditis.
