This study showed the characteristics of scabies patients at the admission date in nosocomial environment comparing control group. Previous long-term care facility admission alone was significantly associated with scabies infection in those patients. Patients with scabies infection were more incommunicable, bedridden status, more in medically severe status although these variables were not significant after adjustment.
Long-term care facility was associated in previous researches albeit the circumstances was different according to the country. In Taiwan, living in a nursing home was confirmed as a risk factor for scabies in a tertiary hospital with bedridden status, indwelling catheter, clinical severe status . In Japan, rapid turnover of patients was risk factor among psychiatric and long-term care hospitals . Dementia history was a risk factor in another report from Japan. Besides national differences or study design, long-term care facilities are variously operated and heterogenous in private medical sector, making it difficult to generalize. In patients with long-term care facility admission history, additional attention to scabies might help early diagnosis. We tried a couple of definition of long-term care facility history such as long-term care facility admission within 1 year, during the lifetime, or direct transfer from it. These definitions showed no statistical difference, so we selected the simplest definition, long-term care facility admission within 1 year.
Dermal screening for all the residents of long-term care facility is not a solution to prevent scabies introduction to acute care hospital. Because of incubation period, scabies patients do not necessarily develop symptoms at the time of admission. Sensitivity of skin scrapes is limited because the number of adult mite on a human with ordinary scabies is low and fewer than 15 . The sensitivity of microscopic diagnosis might be even lower when the exam was not done from a clearly suspected lesion. Based on our results, scabies patients were very few among many patients who come from long-term care facilities to acute care hospitals. It is difficult to diagnosis all the cases with a low prevalence by a low sensitive test. Therefore, it is necessary to educate health-care workers about atypical presentation and pay attention to skin of patients practically. Particularly in patients with long-term care facility admission history, thorough skin examination and include scabies in the differential diagnosis of all the patients with pruritic skin lesion, papules, vesicles, pustules, and pruritus would be helpful for early detection of scabies .
There are limited reports about regional data of scabies prevalence in long-term care facilities. A Japanese research reported 41% of psychiatric and long-term care hospitals experienced scabies in 2004 . Another Canadian report reported 25% of 130 chronic healthcare institutions experienced scabies cases during a one-year period .. A following study about regional data on prevalence of scabies in long-term care facility would help assessing region-specific risk of scabies in medical environment.
Interestingly, patients with scabies were medically severe at the admission date and more admitted via emergency department. Patients with severe status need intensive acute treatment and it is hard for scabies to get attention in this situation. Overcrowding and time constraints were reported as risk factors of missed diagnosis of scabies during emergency department stay in another study . It might be burdensome to check many risk factors in a situation of acute medical care for medically severe patients. We confirmed the other variables were not independent each other. In that aspect, this study is meaningful for identifying a single independent risk factor that can be used to suspect scabies in a hospital environment.
This study has limitation from the retrospective nature. In particular, skin lesion and itching symptom was reported in the scabies group more than 70%, it was detected while scabies infection was suspicious and diagnosed, not at the time of admission. Only limited information was extracted from the admission note, and it might reflect that medical staff cannot afford to take a meticulous examination of skin lesion during the admission process, which gives reason for elucidating representative risk factors of scabies infection in these patients.
In conclusion, scabies infection in acute medical environment is associated with patient`s previous long-term care facility admission.