Validity of First-Time Diagnoses of Inherited Ichthyosis in the Danish National Patient Registry and the Danish Pathology Registry

Increased cancer incidence among patients with hidradenitis suppurativa - a Danish nationwide register study 1977-2017

BACKGROUND

The chronic, inflammatory skin disease hidradenitis suppurativa (HS) (prevalence: 0.5%-1%, diagnostic delay: 7-10 years) primarily arises in younger adults and frequently coincides with autoimmune comorbidities and unhealthy life-styles (smoking and obesity). These factors are known to increase cancer risk, but despite this, information on cancer occurrence among HS patients is scarce.

MATERIALS AND METHODS

A nationwide retrospective register-based study assessing relative risk of cancer - overall and by anatomical site - following HS diagnosis expressed as standardized incidence ratios (SIRs), which is ratios between observed cases among all Danes diagnosed with HS since 1977 and expected cases based on cancer incidence rates of the entire Danish population during the same period.

RESULTS

Participants consisted of a cohort of 13,919 Danes with HS, who during an average of 14.2 years of follow-up developed a total of 1,193 incident cancers, corresponding to a 40% increased risk (SIR = 1.4, 95% CI: 1.3 to 1.4, p < 0.001). Increased risks were observed for cancers of the respiratory system, oral cavity and pharynx, digestive organs and peritoneum, urinary tract, and the lymphatic tissues.

INTERPRETATION

These findings underline an unmet need for health monitoring, lifestyle interventions and cancer screening if and when relevant.

Incidence and Prevalence of 73 Different Genodermatoses: A Nationwide Study in Sweden

This retrospective registry-based cohort study aimed to estimate the incidence and prevalence of genodermatoses in the Swedish population and to analyse associated healthcare usage. Patients diagnosed with genodermatoses were identified from the patient registry of Sahlgrenska University Hospital (Gothenburg, Sweden) between 2016 and 2020. Clinical data from medical records were used to verify diagnoses recorded in the National Patient Registry (NPR). The NPR was then searched for International Classification of Diseases, Tenth Revision (ICD-10) codes Q80-82 and Q84 from 2001 to 2020. The local cohort included 298 patients with 36 unique genodermatosis diagnoses. Verification of these diagnoses in the NPR showed positive predictive values of over 90%. The NPR search yielded 13,318 patients with 73 unique diagnoses, including ichthyoses (n = 3,341; 25%), porokeratosis (n = 2,277; 17%), palmoplantar keratodermas (n = 1,754; 13%), the epidermolysis bullosa group (n = 1011; 7%); Darier disease (n = 770; 6%), Hailey-Hailey disease (n = 477; 4%) and Gorlin syndrome (n = 402; 3%). The incidence and prevalence of each diagnosis were calculated based on the nationwide cohort and are reported. A total of 149,538 outpatient visits were registered, a mean of 4.6 visits per patient. This study provides a valuable resource for the epidemiology of genodermatoses by reporting on the incidence and prevalence of 73 different genodermatoses.

Validity of First-Time Diagnoses of Darier's Disease in the Danish National Patient Registry

Purpose

Darier's disease (DD) is a rare genetic skin disease, characterized by yellow-brown, scaly, crusted papules in seborrheic areas and specific nail changes. This study aimed to validate all first-time diagnoses of DD in Danish National Patient Registry (DNPR). The intent of the study is validation of DNPR for epidemiological and clinical studies on DD.

Patients and Methods

We identified all patients in DNPR who received their first-time diagnosis of DD between January 1, 1977 and December 31, 2018 (International Classification of Diseases [ICD]-8 code 75721 until the end of 1993: ICD-10 code Q828F thereafter). We restricted to diagnoses from departments of dermatology, where these patients are managed. We validated diagnoses against information from medical records, using predefined data extraction sheets and validation criteria. We classified diagnoses as probable when characteristic clinical features were present; confirmed when there was also genetic confirmation, histopathological confirmation and/or positive family history, or rejected (remaining patients). We estimated positive predictive values (PPVs) with 95% confidence intervals (CIs) for diagnoses overall and stratified by ICD classification, sex, age at diagnosis, year of diagnosis, type of diagnosis, and type of contact.

Results

We identified 277 first-time diagnoses of DD, of which 229 (82.7%) stemmed from departments of dermatology. Medical records were available for 196 (85.6%) of these. The overall PPVs for probable and confirmed DD were 89.3% (95% CI: 84.2–92.9) and 81.1% (95% CI: 75.1–86.0), respectively. The PPV for probable ICD-8 diagnosis (95.8% (95% CI: 82.1–99.5)) was slightly higher than that of probable ICD-10 diagnosis (88.4% (95% CI: 82.7–92.3)).

Conclusion

The validity of first-time diagnoses of DD recorded by departments of dermatology in the DNPR is relatively high, making DNPR suitable for epidemiological studies on DD in Denmark, as well as a useful source for recruitment to clinical studies on DD.