The differential diagnostic capacity of serum amyloid A protein between infectious and non-infectious febrile episodes of neutropenic patients with acute leukemia.

We studied the behavior of four major acute phase proteins (SAA, CRP, ACT and AGP) in pyrexial occurrences of 16 neutropenic patients with acute leukemia. Altogether 37 febrile episodes were recorded; 27 were infectious in origin (microbiologically documented infection and clinically documented infection, MDI/CDI group) and 10 were pyrexias of unknown origin (PUO group). In the MDI/CDI group the mean value for the highest individual SAA concentration was 282 +/- 161 mg/l and in the PUO group 95 +/- 79 mg/l. The corresponding mean values were 4.0 mg/l (range 0.2-5.5 mg/l) in 10 control patients with 1 year remission and 0.8 mg/l (range < 0.1-1.2 mg/l) in 30 healthy adults. The peak value of SAA rose above 100 mg/l in 85% of our MDI/CDI pyrexias and in 40% of PUO. More reliable results were obtained when the difference between the value on the day when pyrexia occurred and the previous day was calculated. In that case, the difference was above 75 mg/l in 23 of 27 (85%) MDI/CDI pyrexias and in none of 10 (0%) PUO. In the MDI/CDI group the mean difference was 204 +/- 137 mg/l while it was only 26 +/- 19 mg/l in the PUO group. The statistical significance was very high (p < 0.0001). The CRP monitoring was very inferior to SAA while ACT and AGP monitorings were unsatisfactory.