Nailfold capillary density as a possible indicator of pulmonary capillary loss in systemic lupus erythematosus

ABSTRACT

Nailfold capillaries are involved in the disease process in systemic lupus erythematosus [SLE]. The same pathology is also observed in alveolar capillaries. To correlate the nailfold capillary density with pulmonary KCO function tests and therefore with pulmonary capillary loss in SLE patients. We studied 25 systemic lupus erythematosus patients [22 females and 4 males] and 10 healthy age and sex matched volunteers as a control group. Nailfold capillary density abnormalities were studied using a Leica light microscope under immersion oil at a magnification of x200. Pulmonary KCO function tests were performed within 6 months of measuring nailfold capillary density. The pulmonary diffusing capacity [DLCO] was calculated using the single breath method. Pulmonary diffusing coefficient [KCO] was also calculated and expressed as a percentage of the predicted value. KCO was used as a measure of alveolar wall capillary density. There was a significant difference in nailfold capillary density between systemic lupus patients and controls. There was a non-significant difference in pulmonary KCO function tests between the two groups. There was a significant relation between nailfold capillary density and pulmonary KCO function tests in SLE patients. We used three methods in determining the nailfold capillary density. The nearest value method showed highly significant difference with pulmonary KCO test [p<0.001]. The other two methods [reproducible and highest nailfold capillary density values] showed significant differences [p<0.01 and p<0.05 respectively]. There were significant differences between nailfold capillary density and laboratory findings, arthritis, photosensitivity, malar flush and oral ulcers. Nailfold capillary density is a simple method that can determine alveolar capillary density in SLE