Infectious diseases are managed by multiple, often intersecting, medical and surgical specialties. The link between infections and dermatology is clear, as the skin acts both as a protective barrier against external pathogens and a window to infections involving internal organs and tissue. Infectious diseases, whether community-acquired, healthcare-associated, or imported, are very common in routine dermatology practice. In Spain, however, dermatologists are typically viewed as being specialists in sexually transmitted infections (STIs), an area in which dermatology has played a leading role since its inception. Regrettably, their role in the management of nonvenereal skin and soft tissue infections is not as well recognized, and they are underrepresented in working groups and expert committees involved in this area.1–3 This situation may explain the lack of clarity about the weight of infectious diseases in dermatology caseloads in Spain, an aspect that has not yet been studied in our country. The 2016 DIADERM study was designed to ascertain the estimated prevalence and associated burden of diseases encountered in Spanish dermatology practice.4 The aim of this study was to analyze the DIADERM findings to estimate the overall weight of nonvenereal infections in outpatient dermatology clinics in Spain.

Observational cross-sectional study of diagnoses made in outpatient dermatology clinics in 2016, with analysis of data collected in 2 periods—January 19–21 and May 18–20—to reflect the coldest and warmest periods of the year. The DIADERM survey was completed anonymously by a random sample of dermatologists from the different geographic branches of the Association of Dermatology and Venereology (AEDV) to ensure a representative sample across Spain. The data analyzed in the current study were extracted from this survey. The survey methodology and characteristics (including the data collected and coding system used) are described in detail in the first report on this project.5 The sampling design—random sampling with geographic stratification—was taken into account in the analysis of data. For this study, infectious disease diagnoses were identified using codes from the International Classification of Diseases, Tenth Revision (ICD-10). Codes corresponding to predominantly STIs were excluded.

Our findings indicate that Spanish dermatologists diagnosed an estimated 16190 nonvenereal infections (95% CI, 9338–23Y042) in a typical 5-day working week, a figure that accounted for 9.33% of the overall dermatology caseload. The diagnostic groups are shown by frequency in Table 1. The most common groups were viral warts outside the anogenital region (7475, 46.17% of infections), dermatophytoses (3336, 20.61% of infections), and other viral infections including those caused by Molluscum contagiosum (1592, 9.84%). The distribution of causative agents is shown in Fig. 1; 61.02% of the estimated cases were due to a virus.

Figure 1.

Distribution of nonvenereal infections according to causative agent.

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Nonvenereal infections are compared with other diagnoses in Table 2. Infections were the most common reason for initial visits (84%) and were less common in follow-up visits (48%) and warmer months (44%). Nonvenereal infections differed significantly from noninfectious diseases in terms of patient age (they were more common in adults, 25% vs. 10%, P<.00001) and health care sector (more common in private practices, 39% vs. 31%, P<.0020).

No differences were observed for patient origin or destination in either the public or private health sector (Table 3). Although access to specialist dermatology care is usually direct in the private sector, direct visits were less common for infections than for other diseases (69% vs. 75%) in our series. Referrals from other specialists, by contrast, were more common (4% vs. 3%). In the public sector, direct (emergency room) visits were more common among patients with infections 15% vs. 10%), while referrals from dermatologists were less common (29% vs. 43%).

This analysis of the DIADERM survey findings shows a high prevalence of nonvenereal infections in outpatient dermatology clinics in Spain. These infections were the third most common reason for visits (9.33%), behind actinic keratosis and nonmelanoma skin cancer.5 There was a predominance of viral infections, in particular extragenital human papillomavirus (HPV) infections, and a higher frequency of diagnoses in adults and private practice. This study is the first of its kind to shed greater clarity on the spectrum and burden of nonvenereal infections in outpatient dermatology clinics in Spain.

In a study of referral patterns for skin diseases at an outpatient dermatology clinic in Denmark, Kiellberg and Sand6 found that infections accounted for 13.1% of all referrals. The clinic, however, is an acute care clinic that processes referrals within an average of 24–48hours. This immediacy possibly explains why infections accounted for more diagnoses than in our study.7 As to be expected in an acute care setting, bacterial skin infections were the most common type of infection.6 In the 2013 Global Burden of Disease Study, skin diseases accounted for 1.79% of the global burden, measured in disability-adjusted life years. Five of the 10 skin diseases with the largest burden had an infectious origin: viral skin diseases, fungal skin diseases, scabies, pyoderma, and cellulitis.8 In Spain, although data are unavailable for specialist dermatology practice, studies of reasons for primary care visits have shown that skin infections account for 10% to 20% of all dermatology-related visits.9,10 The overall prevalence, however, is probably higher, as the diagnostic codes for bacterial skin infections were not included in these studies.

Most clinical guidelines and consensus statements addressing skin and soft tissue infections refer exclusively to bacterial infections.11–13 This is probably because of the wide use of this term in hospital settings, where most skin infections requiring hospitalization are acute infections caused by bacteria.14–16 Dermatomycosis and HPV infections are the main skin infections described in both primary care and dermatology outpatient settings.9,10,17,18 Our findings are consistent in this regard, as the 2 main diagnoses in our study were extragenital viral warts and dermatophytoses. The predominance of these diagnoses in primary and specialist care settings is probably due, at least in part, to the subacute or chronic nature of these conditions, with patients following standard referral pathways. Cause of skin infections can vary widely geographically due to climate-related or ethnic-social factors.19–21

Skin infections are largely representative of diseases associated with high resolution rates in outpatient settings. In other words, patients typically receive a diagnosis, treatment, and clinical report in a single day.22 This process favors the flow of patients and the dynamics of general dermatology clinics. According to our analysis of the DIADERM survey findings, patients with an infection are more likely to be directly discharged than those with other types of diseases, possibly due to the ability of dermatologists to effectively resolve these cases.

Considering the above, it would seem reasonable for infections to occupy a prominent position in dermatology, not just for quantitative reasons (they are the third most common reason for outpatient visits in our field), but also for qualitative reasons, as proper diagnosis and treatment by a dermatologist will probably save overall time and resources and improve patient perception of care.

Although this study has the strength of a nationwide study, with a representative sample of dermatologists and outpatient dermatology practice across Spain, it has some limitations. One is the low prevalence of bacterial infections recorded, which could cast doubts about the involvement of dermatologists in the diagnosis and management of bacterial skin infections in outpatient settings. We believe that this low prevalence may be related to the typically acute course of bacterial infections, which are largely diagnosed and treated in emergency departments. Several studies have ranked bacterial infections as the leading cause of infection-related emergency department visits in Spain.23,24 It should also be noted that because the DIADERM survey was conducted in 2016, its findings will not reflect recent changes in the incidence of certain infections or infestations, such as scabies and tinea capitis.25–27 Finally, by excluding STIs, we will probably have underestimated certain diagnoses such as HPV infections and pediculosis due to overlapping ICD-10 codes. (This issue was identified by Martín-Gorgojo et al. in their study of the weight of STIs in dermatology caseloads within the DIADERM study.28) Nonetheless, we decided to exclude these epidemiologically well-studied infections as we wished to obtain a faithful estimate of the weight of nonvenereal infections in outpatient dermatology practice in Spain. The decision to distinguish between venereal and nonvenereal infections, however, was not purely academic, as we also believe that venereology is already a strong, well-established area within the field of dermatology.

Nonvenereal infections are an important part of routine dermatology practice. They have a large weight in overall caseloads, and there is a close link between etiology and routes by which patients access outpatient dermatology clinics. Clinical research projects and greater interaction with other specialties will provide greater insights into the impact of infectious diseases and help position dermatologists as authorities in all infections involving the skin.

The DIADERM study is an initiative of the AEDV and has received funding from the pharmaceutical company Novartis. Novartis did not participate in the collection or analysis of data or the interpretation of results.

The authors declare that they have no conflicts of interest.