Serum neopterin for early assessment of severity of severe acute respiratory syndrome

Abstract

Neopterin and C-reactive protein (CRP) concentrations were determined in serum samples from 129 severe acute respiratory syndrome (SARS) patients and 156 healthy blood donors. In the patients with confirmed SARS, an early neopterin elevation was detected already at the day of onset of symptoms and rose to a maximum level of 45.0 nmol/L 3 days after the onset. All SARS patients had elevated neopterin concentrations (>10 nmol/L) within 9 days after the onset. The mean neopterin concentrations were 34.2 nmol/L in acute sera of SARS patients, 5.1 nmol/L in convalescent sera, and 6.7 nmol/L in healthy controls. In contrast, the mean CRP concentrations in both acute and convalescent sera of SARS patients were in the normal range (<10 mg/L). Serum neopterin level in SARS patients was associated with fever period and thus the clinical progression of the disease, while there was no significant correlation between the CRP level and the fever period. Serum neopterin may allow early assessment of the severity of SARS. The decrease of neopterin level was found after steroid treatment, which indicates that blood samples should be collected before steroid treatment for the neopterin measurement.

Fig. 1

Serum neopterin and C-reactive protein (CRP) concentrations in different groups of the population. (a) Neopterin concentrations as determined by ELItest® Neopterin-Screening and (b) CRP concentrations as determined by in-house ELISA in (I) healthy subjects and in (II) acute sera or (III) convalescent sera of SARS patients. The lines inside the boxes denote medians; the boxes indicate the interval between the 25th and 75th percentiles. The whiskers denote the interval between the 10th and 90th percentiles. The small squares (□) denote the means and the dashes (-) denote the maximum and minimum values. The difference in neopterin concentrations between the groups is statistically significant (P < 0.001, Mann–Whitney test).

Fig. 2

Serum neopterin (▲) and CRP (■) concentrations (mean ± SEM) in 129 SARS patients after the onset of symptoms expressed as days (D), weeks (W), and months (M); the normal ranges of neopterin and CRP levels are <10 nmol/L and <10 mg/L, respectively (grey area).

Fig. 3

Relationship between the fever periods of SARS patients and (a) serum neopterin or (b) serum CRP concentrations detected (A) 1–2 days, (B) 3–4 days, (C) 5–6 days, and (D) 7–8 days after the onset.

Fig. 4

Relationship between serum neopterin concentrations detected 1–2 days, 3–4 days, 5–6 days, and 7–8 days after the onset and the antibody levels in convalescent sera (collected after 15 days of the onset) of these SARS patients determined by IFA.

Fig. 5

Serum neopterin level (mean ± SD) in the patients with (n = 69) or without (n = 53) steroid therapy when the serum samples were collected (*P < 0.05, **P < 0.01; the number of patients in each group is indicated in the bottom line).