Comparison of diagnostic spectrum between inflammation of unknown origin and fever of unknown origin: A systematic review and meta-analysis

BACKGROUND

Patients with inflammation of unknown origin (IUO) and fever of unknown origin (FUO) are commonly considered a single population. Differences in underlying causes between both groups may steer the diagnostic work-up.

METHODS

PubMed, Embase, Web of Science, and ClinicalTrials.gov were searched from July 2009 through December 2023. Studies including both FUO and IUO patients with a sample size of ≥20 were considered. The primary outcome was the difference in the rate of patients affected by predefined diagnostic categories according to meeting FUO or IUO criteria. Data were pooled using random-effects models.

RESULTS

A total of 8 studies met criteria for inclusion, with a total of 1452 patients (466 with IUO and 986 with FUO). The median rate of IUO patients among the included studies was 32 % (range 25-39 %). Patients with IUO had a lower likelihood of infection (OR 0.59 [95 % CI; 0.36-0.95]; I2 0 %). There were no significant differences in the rate of noninfectious inflammatory disorders, malignancies, miscellaneous disorders, or remaining undiagnosed. Comparison of diagnostic subgroups revealed that IUO patients were less likely to have systemic autoinflammatory disorders (OR 0.17 [95 % CI, 0.05-0.58]; I2 42 %) and more likely to have vasculitis (OR 2.04 [95 % CI, 1.23-3.38]; I2 21 %) and rheumatoid arthritis or spondylarthritis (OR 3.52 [95 % CI, 1.16-10.69]; I2 0 %).

CONCLUSION

Based on our findings, there is little reason to assume that FUO and IUO patients would benefit from a different initial diagnostic approach.

LPS-Induced Release of IL-1β, IL-1Ra, IL-6, and TNF-αin Whole Blood from Patients with Familial Hypercholesterolemia: No Effect of Cholesterol-Lowering Treatment

Proinflammatory cytokines, such as interleukin-1beta (IL-1beta), IL-6, and tumor necrosis factor-alpha (TNF-alpha), are suggested to have an important role in the process of atherosclerosis. Patients with heterozygous familial hypercholesterolemia (FH) have a marked elevation in the plasma level of low-density lipoproteins (LDL), and they show early development of atherosclerosis. The aim of the present study was to test with a whole blood culture system if hyperlipoproteinemia is associated with increased cytokine production capacity in these patients and if treatment with 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors influences this production capacity of blood cells, at both the protein and mRNA levels. The capacity of blood cells in a whole blood culture to produce IL-1beta, IL-6, TNF-alpha, IL-12, IL-18, and IL-1 receptor antagonist (IL-1Ra) in response to lipopolysaccharide (LPS) appeared to be similar for heterozygous FH patients and healthy volunteers. Furthermore, the capacity to produce IL-1beta, IL-6, and TNF-alpha in response to LPS was not modified by cholesterol synthesis inhibitors at the level of mRNA expression or at the level of release. On the other hand, the release of IL-1Ra was significantly increased after treatment with HMG-CoA reductase inhibitors, although only at the protein level. This suggests a possible beneficial anti-inflammatory role for this therapy.

LPS-induced cytokine production and expression of beta2-integrins and CD14 by peripheral blood mononuclear cells of patients with homozygous familial hypercholesterolemia

It has been suggested that proinflammatory cytokines such as tumor necrosis factor-alpha (TNF) and interleukin-1beta (IL-1), as well as adhesion molecules such as beta2-integrins and CD14, play a role in the pathogenesis of atherosclerosis. Familial hypercholesterolemia (FH) is an autosomal disease in which defective or absent LDL receptors are the cause for extreme LDL concentrations and early development of atherosclerosis. We studied lipopolysaccharide-induced cytokine production and the expression of adhesion molecules by mononuclear cells of three homozygous FH patients and compared them with first-degree relatives and healthy controls. There was a tendency towards increased cytokine production by cells of FH patients, whereas the expression of adhesion molecules was not modified compared to controls. In addition, LDL-apheresis inhibited IL-1 and TNF production and the expression of CD11a, CD11b, CD11c and CD14 by the mononuclear cells of FH patients and this may be an additional beneficial effect of LDL-apheresis apart of decreasing LDL concentrations.

LPS-induced cytokine production and expression of LPS-receptors by peripheral blood mononuclear cells of patients with familial hypercholesterolemia and the effect of HMG-CoA reductase inhibitors

Inflammatory processes play an important role in atherogenesis, and proinflammatory cytokines such as interleukin-1beta (IL-1beta), IL-6, and tumour necrosis factor alpha (TNFalpha) are thought to be mediators in this phenomenon. We have previously established that peritoneal macrophages of LDL-receptor knock-out mice, which are hypercholesterolemic and are prone to atherosclerosis, have an increased LPS-induced cytokine production capacity, ex vivo. The aim of the present study was to investigate whether the process leading to atherosclerosis in patients with familial hypercholesterolemia (FH) is associated with increased cytokine production capacity of peripheral blood mononuclear cells (PBMC) and/or increased expression of adhesion molecules on monocytes and lymphocytes. Furthermore, we assessed the effect of cholesterol lowering on the production capacity of PBMC, as these drugs are beneficial with regard to cardiovascular diseases. LPS-induced IL-1beta and TNFalpha production by PBMCs of 21 heterozygous FH patients appeared to be similar to the production by PBMCs of 21 healthy volunteers. In addition, expression of the LPS-receptors CD14 and beta2-integrins in nine patients and controls did not differ either. In a second series of experiments, HMG-CoA synthesis inhibitors were ineffective to change the LPS-induced production by PBMC of IL-1alpha, IL-1beta, IL-1 receptor antagonist (IL-1ra), IL-6, and TNFalpha. In conclusion, cytokine production capacity of blood cells or the expression of LPS-receptors on circulating PBMC do not deviate in subjects with FH and also do not change as a result of treatment with cholesterol synthesis inhibitors.