Antistreptolysin O titre (ASO or ASLO) is the measure of the rate of antibodies processed by the body after contact with streptolysin O produced by streptococcus.
It is the serological test used for the diagnosis of beta-haemolytic Streptococcus type A infection.

The titre becomes positive one week after infection, reaches its peak after about 3-5 weeks, then decreases in the following months.

The titer expresses an ongoing or past antibody response evoked by a series of antigens present in beta-haemolytic Streptococcus type A.

Normal values

v.n. < 200 Ul

Increase values

Streptococcal infections (rhinitis, pharyngitis, tonsillitis, otitis, sinusitis, impetigo contagiosa, tooth granuloma, paronychia)
Scarlet fever
Erythema nodosum
Rheumatic endocarditis
Acute articular rheumatism
Acute glomerulonephritis
Erysipelas
Primary chronic polyarteritis
Bechterew’s disease

False positives

Cholestasis
Pulmonary tuberculosis
Hypercholesterolemia