Blood Tests for Inflammation Can Be Discordant

The erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) levels are widely used tests of inflammation that sometimes show opposite results.

However, CRP and ESR may not correlate substantially in some conditions, and the extent to which CRP and ESR results agree with each other in an unselected patient population is not clear in clinical practice, as the results of the two tests are sometimes different.

Scientists at the Texas Health Presbyterian Hospital (Dallas, TX, USA) performed 2,150 paired CRP/ESR measurements in 1,753 patients, between January and December of 2011. There were 1,731 patients who were not pregnant and were all adults aged 18 years or more. Initial CRP and ESR results for each patient were divided into quartiles.

The CRP assay performed is based on a reaction between CRP in a serum or plasma sample and polyclonal anti-CRP antibodies that have been adsorbed to latex particles the Multigent CRP Vario Reagent, (Sentinel; Milan, Italy). Agglutination is detected as an absorbance change at 572 nm on the Architect c8000 (Abbott Laboratories; Abbott Park, IL, USA). The ESR assay samples are read with an ESR-Auto Plus instrument in QuickMode (Streck; Omaha, NE, USA) and converted to Westergren units. The results can range from zero to greater than 120 mm/hour.

The ages of the 105 patients in the high CRP/low ESR–discordant group and the 107 in the high ESR/low CRP–discordant group were similar. The high CRP/low ESR–discordant group had more patients with infections than the high ESR/low CRP–discordant group particularly infections in the urinary tract, gastrointestinal tract, lungs and bloodstream. However, they had fewer bone and joint infections than the high ESR/low CRP–discordant group.

Connective tissue diseases, such as systemic lupus erythematosus, were less common in the high CRP/low ESR–discordant group than in the high ESR/low CRP–discordant group. Ischemic strokes or transient ischemic attacks almost invariably occurred in the high ESR/low CRP–discordant group, whereas myocardial infarction or venous thromboembolism was limited to the high CRP/low ESR–discordant group. The authors concluded that their findings will provide information to physicians who order these two tests together and receive discordant results, which occurs in approximately one in eight patients. The study was published on August 23, 2012, in the journal Translational Research.

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