A total of 67 patients were randomly selected from those fulfilling the 1990 American College of Rheumatology (ACR) criteria for FM, who first visited our outpatient clinic; 30 age- and sex-matched healthy controls were also included in this study.

Clinical parameters included tender point count, Fibromyalgia Impact Questionnaire (FIQ) score [7], arthralgia, headache, sensations of numbness or coldness, irritable bowel syndrome, dry eyes, and dry mouth. The FIQ comprises 10 brief, self-administered scales as follows: physical impairment, feeling good, missing work, completing work, pain, fatigue, feeling rested, stiffness, anxiety, and depression.

Before the nailfold test, patients were seated inside the procedure room for a minimum of 15 minutes to adapt to the room temperature of 20℃ to 25℃. Each patient was seated such that the dorsum of their hand was facing upwards, with halogen lights illuminating the nails (coated with immersion oil) under nailfold microscopy. The NFC test was performed by a skilled examiner who was not aware of the patients' clinical status. Patients' nailfolds, of the second, third and fourth digits of both hands, were observed under a light microscope (×100 and ×400 magnifications; Olympus SZ-PT, Olympus, Tokyo, Japan). A digital camera (Polaroid, Minnetonka, MN, USA) transmitted all microphotographs to a computer; after the images were saved, they were enhanced using color filtering via the Adobe Photoshop version 7.0 (Adobe Systems Inc., San Jose, CA, USA). For quantitative analysis, we counted the total number of capillaries, and the number of deletions, within a 3-mm-wide area of the central part of the digits [8]. The outcomes were recorded as average values for six digits. Furthermore, an experienced rheumatologist measured the apical limb width, and the capillary width, of three capillary rings located at the center (where the resolution is most-fine), directly from a computer screen and from all six digits. By measuring the capillary boundary at a capillary length of 25 µm (1 cm; ×400) we defined the capillary dimension as the total number of pixels in the designated area (Fig. 1) [6], using the Adobe Photoshop version 7.0.

All results are expressed as median values and interquartile ranges. For statistical analysis, the SPSS version 13.0 (SPSS Inc., Chicago, IL, USA) was used. We used the Mann-Whitney U test to compare NFC parameters and FIQ scores; Fisher exact test and the chi-square test were used to compare clinical manifestations between the FM patient and control groups. Spearman correlation coefficient was used to assess the relationship between NFC measurement parameters and FIQ scores. A p < 0.05 was taken to indicate statistical significance.

We included a total of 67 FM patients and 30 healthy controls. The mean age of the 67 FM patients was 41.97 years, compared to 37.26 years in the 30 healthy controls. There were 63 females (94%) in the FM group; all 30 healthy controls were female. Mean body mass index was marginally higher in the FM group (22.46 kg/m²) compared to the control group (21.9 kg/m²). A total of six FM patients (8.96%) had Raynaud's phenomenon, which represents a significantly higher prevalence rate compared to that of the control participants (none of whom had Raynaud's phenomenon). The mean duration of Raynaud's phenomenon in the FM group was 8.1 months (Table 1).

The most frequent symptom observed in the FM group was arthralgia (n = 47, 70.1%) followed by headache (n = 39, 58.2%), numbness (n = 38, 56.7%) and peripheral coldness (n = 34, 50.7%). Other symptoms or syndromes in the FM patients included irritable bowel syndrome (n = 31, 48.3%), dry eye (n = 20, 29.9%), and dry mouth (n = 15, 22.4%). More than 50% of the FM group were full-time housewives; 41 of this group (61.2%) were working from home, whereas 26 (38.8%) had other occupations. Six (9.0%) of these FM patients were employees, three (4.5%) were laborers, five (7.5%) were operators, and 12 (70.1%) had other jobs. A total of 47 (70.1%) FM patients were married and 24 (35.8%) were postmenopausal (Table 2).

FIQ was designed to assess the current health status of FM patients across diverse domains, including physical function and symptoms. The FIQ consists of 10 subscales, the first of which comprises 11 items related to the performance of physical functions that require significant muscular exertion. The second and the third subscales are concerned with the number of days on which patients felt well, and the number of days on which they were unable to work (including housework) due to FM symptoms. Subscales 4 to 10 represent horizontal linear scales assessing work difficulty, pain, fatigue, morning tiredness, stiffness, anxiety, and depression [9]. Our FM groups completed the FIQ subscales concerned with their physical functionality and symptoms (Table 3).

We conducted the NFC test on both the FM and healthy control groups. The FM patients had an average of 17.3 ± 1.7 loops in the 3-mm-wide area of the central part of their digits, compared to an average of 21.8 ± 2.9 loops in the control group. The average number of loop deletions was 2.2 was 2.2 ± 0.9 in the FM group, compared to 0.6 ± 0.7 in the healthy controls (Table 4). It appears that FM patients had a lower number of capillaries, but higher deletion scores compared to the healthy controls on NFC. The average apical width (µm) of the FM patients was 1.1 ± 0.2; their mean capillary width (µm) was 5.4 ± 0.5. In the control group, the average apical width was 3.7 ± 0.6; their capillary width was 7.7 ± 1.4 (Table 4). Both apical limb and capillary width were significantly decreased in FM patients, indicating that FM patients have abnormally decreased digital capillary diameter and density.

However, capillary dimension (total number of pixels measured using Adobe Photoshop) did not differ between the FM and control groups. The mean capillary dimension of the FM group was 524.1 pixels; in the control group it was 515.7 pixels (Table 4). This suggests that the length or tortuosity of capillaries in FM patients is increased to compensate for diminished microcirculation.

To compare the FIQ scores of each group with their NFC results, we assessed the correlations between clinical manifestations and NFC parameters; as shown in Table 5, among the FIQ parameters, only subscale 1 (physical function) was negatively correlated with capillary dimension (r = -0.248, p = 0.048); there were no other significant associations between NFC patterns and other FIQ subscale scores.