Differential diagnosis of elevated erythrocyte sedimentation rate and C-reactive protein levels: a rheumatology perspective.

OBJECTIVE: In the case of high erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) levels, the diagnosis of the underlying disease can be challenging especially in serologically unrevealing patients who have nonspecific clinical findings. We aimed to investigate the final distribution of definitive diagnoses in patients who initially presented with nonspecific clinical findings and sustained elevations in serum ESR/CRP levels.
MATERIAL AND METHODS: The medical records of patients hospitalized in a rheumatology clinic between January 2010 and January 2011 were retrospectively analyzed. The patients were classified into two main groups: those with previously diagnosed underlying rheumatic disease (RD) and those without. The groups were analyzed for the final distribution of definitive diagnoses.
RESULTS: Out of 112 patients in the general study population, 47 had a previous RD and 65 had no previous history of RD. In these 65 patients, the most common etiology of nonspecific elevations in ESR/CRP levels was new onset RD (52.3%). Polymyalgia rheumatica (PMR) was the most common new onset RD (38% of all new onset RD) followed by seronegative rheumatoid arthritis. The incidences of infections and malignancies were 24.6% and 9.2%, respectively. CRP levels were significantly higher in infections when compared with new onset RD or malignancies (p<0.05). In patients with previous RD, the flare of the underlying disease was the most common etiology of nonspecific elevations in ESR/CRP levels (n=39, 83%, 20 female/19 male).
CONCLUSION: Extraordinarily high levels of serum CRP in a patient with nonspecific clinical findings should raise suspicion for non-rheumatic diagnoses, such as infection and malignancy, even in the presence of a previously diagnosed RD. Advanced radiological investigation is justified in these cases to rule out malignancy.