This study identified five factors via EFA. These five factors were insufficient energy/vitality, cardiac–pulmonary distress, sleep disturbances, musculoskeletal distress, and gastrointestinal distress. They were similar to the clusters identified by Yu IC, Huang JY and Tsai YF  which included energy and sensory discomfort, gastrointestinal (GI) and cardiac–pulmonary symptoms, cardiovascular symptoms, and electrolyte imbalance. However, these four clusters identified by Yu IC, Huang JY and Tsai YF  had apparently problems with overlapping (cardiac– pulmonary symptoms, cardiovascular symptoms) and vague dimension (electrolyte imbalance). Furthermore, the characteristics of symptom distress verified in our study were much more similar to those dimensions of energy/vitality, cardiac-related problems, pain/comfort, and gastrointestinal (GI) system proposed by Jablonski's study (2007). Compared to the symptoms clusters verified in our study with those identified by Yu IC, Huang JY and Tsai YF  and Jablonski A , the primary difference was our study separated sleep disturbances as a factor, due to sleep disturbed result from multiple influencing factors presented in patients receiving HD . These influence factors may be related to certain symptom distress like pain/comfort  or sensory discomfort . It may explain why sleep disturbances was not an independent dimension/cluster in the study of Yu IC, Huang JY and Tsai YF  and Jablonski A .
Factor 1, insufficient energy/vitality, was one of the most troublesome distress among the multiple symptoms experienced by patients received HD, it was also found in the study of Yu IC, Huang JY and Tsai YF  and Jablonski A . This symptom distress, insufficient energy/vitality, was directly related to renal anemia due to lack of erythropoietin . In addition, blood loss during hemodialysis and latent gastrointestinal bleeding were also common causes of anemia in patients . When anemia occurred, insufficient numbers of circulating red blood cells were available to transport and release oxygen to tissues, thus, patients were prone to symptoms occurred simultaneously such as vertigo, headache, muscle weakness, tiredness, and lack of vitality .
For patients received HD, ‘cardiac–pulmonary symptoms’ presented in Factor 2 was a common symptom distress, it often resulted from fluid overload. The main reason was patients’ poor water control during dialysis sessions. When patients had difficulty to control or restrict their fluid intake, it may lead to excessive weight gain during dialysis sessions (i.e., interdialytic weight gain, IDWG). A poor IDWG often caused hypotension, dry mouth, chest pain, chest tightness, and arrhythmia during dialysis . Moreover, fluid overload may lead to congestive heart failure . which further caused cardiomegaly, resulting in symptom distress such as shortness of breath, dyspnea, bloating and decreased appetite . It explained why the chest pain, shortness of breath, dyspnea, chest tightness, arrhythmia, and lack of appetite were clustered to the dimension of ‘cardiac–pulmonary symptoms’ after conducting the factor analysis.
The symptoms under factor 3 included waking in the night, trouble falling asleep and itchy skin, those clustered into a factor called ‘sleep disturbances’. Patients with ESKD often experienced restless leg syndrome resulted from urotoxic peripheral neuropathy. The patient frequently felt uncomfortable at night or when lying in bed, especially on a quiet night. These feelings included insect crawling, acupuncture, or deep itchiness, those made patient had to keep moving their feet or get up to walk to gain a little relief, it resulted an interrupted sleep [26, 27]. In addition, uremic pruritus caused by calcium and phosphorus deposition may be another factor affecting patients' sleep. It was a chronic, uncomfortable symptom and worsened at night, it caused severe negative effect on the patient's sleep . It explained why waking in the night, trouble falling asleep, and itchy skin synthesized into a new dimension called ‘sleep disturbances’.
For patients receiving hemodialysis, electrolyte imbalance was a common issue. Calcium and phosphorus imbalance was one of the electrolyte imbalances; it often caused secondary hyperparathyroidism, and patients were prone to complications of renal osteodystrophy . Renal osteodystrophy caused symptoms distress, such as joint pain and muscle weakness; and Hyperkalemia was also a common electrolyte imbalance due to kidney failure. Potassium ion balance was essential for nerve conduction and muscle contraction. Hyperkalemia caused depolarization of skeletal muscle cell membranes and inhibit skeletal muscle excitement; and caused muscle numbness, sore, and weakness in the limbs . Through factor analysis, joint pain, sore muscles, and numbness were clustered to be a new dimension called ‘musculoskeletal symptoms’.
Gastroparesis was a distress for patients receiving HD due to autonomic neuropathy; it prolonged the time to empty their stomach and caused discomfort symptoms, such as nausea, vomiting, and lack of appetite . In addition, Patients receiving HD took the medication of phosphorus binders due to renal osteoporosis. This kind of medication often produced gastrointestinal side effects, such as nausea, vomiting, and abdominal pain . Severe nausea and vomiting easily leaded to electrolyte imbalance and caused cramps further. Furthermore, uremic polyneuropathy may be another factor caused patients to cramp; the earliest symptom was muscle cramps in the lower limbs . Therefore, vomiting, nausea, and cramps were synthesized into a factor called gastrointestinal distress.
Cronbach’s alpha coefficients for the HSD-22 total scale (0.93) and each of the five subscales (0.77–0.85) indicated that this newly-constructed instrument had a good internal consistency. The results of test–retest analysis showed that the HSD-22 was relatively stable over a 2–4-week period.
Patient receiving Hemodialysis often experienced multiple symptoms that usually occurred concurrently; a single symptom seldom occurred separately. To provide an effective intervention for symptom distress, a psychometrically robust measurement which captured the essence of symptom clusters under a group of symptoms and shared a common etiology or biomechanics were needed. The HSD-22 developed in this study covered five factors via factor analysis. In these five factors, each factor covered a cluster of symptoms which shared a common etiology or biomechanics discussed above. Therefore, we suggested that the HSD-22 was verified and improved one of the symptom clusters by HPs earlier, it is a valid and reliable scale and can provide a useful clinical assessment tool for healthcare professionals (HPs) working in the HD unit to identify possible symptom clusters of patients undergoing HD. To achieve more efficacy treatments, clinical interventions should be considered in terms of the common mechanism of symptom cluster.
In our study, participants were recruited from a medical university hospital, even they came from every corner of southern Taiwan, but still restricted to one hospital and they may unable to on behalf of all hemodialysis of the population in Taiwan. And due to the reduced data, we used EFA to analyze the HSD-22 for smaller set of variables and to explore the underlying theoretical structure of a phenomenon, it narrowed construct validity. We suggested that future studies can recruit the participants from overall of Taiwan through multiple medical university hospital, and using confirmatory factor analysis (CFA) to test its construction validity. Then, study result may be more definite.