Background/Purpose:

Increased urinary albumin excretion (UAE) is an early marker of renal microvascular damage that correlates with cardiovascular risk and corresponds to a state of generalized microvascular impairment, even below the threshold values usually considered for microalbuminuria (30-300 mg in a 24h urine sample). However, data regarding prevalence of microalbuminuria are conflicting in patients with rheumatoid arthritis (RA), a disease characterized by excess cardiovascular risk. Moreover, it remains unclear whether it corresponds to a state of generalized microvascular dysfunction in this particular group of patients. We investigated for the first time whether microalbuminuria is associated with other forms of microvascular impairment located in the dermal capillary network, the retinal and the coronary microvasculature.

Methods:

24h urine samples were obtained from RA and non-RA individuals to estimate UAE. Morphological changes in the retinal microvasculature were evaluated from retinal photography. Retinal images were processed with specifically designed computerized software that calculates retinal arteriolar and venular diameters, to obtain central retinal arteriolar equivalent (CRAE) and central retinal venular equivalent (CRVE), as well as their ratio (arteriovenous ratio, AVR). Functional assessment of the coronary artery network was based on measurement of the subendocardial viability index (SEVR), a non-invasive estimate of microvascular coronary perfusion, using radial artery applanation tonometry. Dermal capillary rarefaction was evaluated with nailfold capillaroscopy applied in the distant phalanx of the fingers, using semi automated software that calculates capillary density in the obtained images.

Results:

A total of 111 individuals were studied, of whom 74 were RA patients with long-standing disease [9 (4–16.5) years], moderate disease activity (DAS score: 3.6±1.4), and relatively low levels of systemic inflammation, and 37 were matched controls. Patients with RA presented narrower retinal arterioles, shown by decreased CRAE (78.0±8.9 vs 87.4±10.0 μm, p<0.001) and AVR (0.69±0.10 vs 0.78±0.10, p<0.001); impaired coronary microvascular perfusion, shown by decreased SEVR (140.6±22.3 vs 150.7±21.6 %, p=0.038), and pronounced capillary rarefaction, reflected in a lower number of dermal capillaries per visual field (132.5±28.2 vs 151.2±25.6, p=0.007), compared to controls. By contrast, neither UAE [5.1 (2.8 – 10.8) vs 6.5 (3.0 – 11.7) mg/24h] nor prevalence of microalbuminuria (11.0 vs 8.1%) differed between patients and controls (p=ns for both). In the RA group, UAE was not significantly associated with inflammation or other disease-related parameters, nor with any of the studied microvascular indices of the coronary microcirculation, the retinal microvasculature, and the dermal capillary network.

Conclusion:

In our population of RA individuals, microalbuminuria was not associated with morphological and functional alterations in distal microvascular beds. Increased UAE in RA patients might be primarily considered as a manifestation of compromised function of the renal microvasculature, rather than a marker of generalized microvascular dysfunction.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/microalbuminuria-in-rheumatoid-arthritis-investigating-the-association-with-diffuse-functional-and-morphological-alterations-of-the-retinal-microvasculature-the-dermal-capillary-network-and-the-coro/