# Fluctuations and Changes in Acute Phase Reactive Proteins in Fasting and Nonfasting States

## TL;DR

This study shows that levels of acute-phase reactive proteins change significantly after eating, which could affect clinical test results.

## Contribution

The study reveals clinically significant fluctuations in APRP levels between fasting and nonfasting states, with implications for diagnostic accuracy.

## Key findings

- CRP levels exceeded allowable error thresholds in up to 46% of subjects post-glucose intake.
- IL-6 showed clinically unacceptable fluctuations in 60% of subjects at 30 minutes post-glucose.
- Dietary factors significantly influence APRP test results, impacting clinical interpretation.

## Abstract

In clinical practice, acute‐phase reactive proteins (APRPs) are frequently measured at random times. However, it is unclear whether the use of fasting or nonfasting samples affects results. This study aims to investigate the variations of APRPs between fasting and nonfasting conditions.

This study was conducted based on the oral glucose tolerance test (OGTT) experiment due to standard energy intake and strict time flow. Fifty subjects were enrolled and underwent a 12‐h fasting period before the experiment. Blood samples were collected the following day at baseline (fasting, T0) and 30 (T1), 60 (T2), 120 (T3), 180 (T4) minutes postglucose intake. A total of 250 blood samples were obtained. To quantify clinical fluctuations, percentage bias was calculated, and Bland–Altman plots were employed.

Our observational study demonstrated significant postprandial variations for APRPs. For CRP, 17 (34%) of 50 subjects at T1, 21 (42%) at T2, 23 (46%) at T3, and 16 (32%) at T4 exhibited levels exceeding the maximum allowable error in medical laboratory testing, indicating clinically unacceptable bias. For IL‐6, thirty subjects (60%) at T1, 27 (54%) at T2, 28 (56%) at T3, and 32 (64%) at T4 displayed clinically unacceptable fluctuations. Among other APRPs, the maximum number of subjects exceeding acceptable bias thresholds was 28% (14/50) for procalcitonin, 38% (19/50) for transferrin, 34% (17/50) for prealbumin, and 24% (12/50) for ceruloplasmin.

Clinical fluctuations were observed in the levels of APRPs between fasting and nonfasting states. Clinicians should pay attention to the effects of dietary factors on test results.

This study investigated the clinical changes in acute‐phase reactive protein (APRPs) assays under fasting and nonfasting conditions. The findings revealed significant fluctuations in APRPs levels at different intervals following a standardized diet. Specifically, clinical bias for serum C‐reactive protein (CRP), interleukin‐6 (IL‐6), procalcitonin (PCT), transferrin (TRF), prealbumin (PA), and ceruloplasmin (CER) could exceed maximum allowable error thresholds established by medical laboratories compared with the fasting levels. Consequently, clinicians should be cognizant of dietary influences on test results.