Validation of generalized drug‐related rash diagnoses using International Classification of Diseases 9th and 10th Revision codes

Abstract

Six of the eight patients saw a reduction in PDAI at 6 months with no increase in adjuvant therapy. Patients 1 and 6 had increases in PDAI at 6 months, by 14 and 5 points, respectively, with patient 1 receiving an additional cycle of rituximab. Seven of the eight patients had an available score for PDAI at 12 months, with a reduction seen in all, and a mean improvement from baseline of 90%. The reductions in PDAI are clinically significant given the impact that blistering skin conditions have on quality of life. There was variation in PDAI at baseline between patients, ranging from 4 to 20. This may represent a milder spectrum or partially treated disease, and could have impacted the time to endpoints.The prednisolone dose at baseline ranged from 0 to 25 mg per day (Figure 1). This decreased to a range of 0-5 mg per day at the end of follow-up. All patients saw a decrease in daily prednisolone dose from baseline, with exceptions being patient 6, who remained on 5 mg per day throughout, and patient 7, who was not on prednisolone at baseline.The minimum time at which B-cell subset depletion was observed varied from 75 to 1262 days. Reduction in baseline antidesmoglein levels was seen in all patients following administration of rituximab for varying lengths of time (Figure 1).No serious adverse events occurred in any patients following administration of the 200-mg protocol. Previous adverse events with rituximab have been reported to include infusionrelated reactions and infections. 6,7 In Australia, the use of rituximab in pemphigus is off label. Ultralow-dose rituximab is a cost-effective option and may be particularly useful where cost is a barrier to access. Uncertainty still remains over optimal rituximab dosing in pemphigus, with no formal dose-finding studies to date. Small studies have proposed low-dose and ultralow-dose protocols. 2,8 This study suggests that two infusions of rituximab 200 mg given 14 days apart may be an efficacious and safe option in patients with mild pemphigus disease in conjunction with more traditional adjuvants, and offers an alternative to the 500-mg and 1000-mg dosing protocols.As this study was retrospective there was variation in review timeframes and pathology based on clinical need rather than set intervals. Additional limitations are the small number of heterogeneous patients and lack of controls. Larger prospective randomized controlled trials are required to investigate these findings further.

Higher Odds of Adverse Cutaneous Reactions in Patients With Dermatomyositis Treated With Hydroxychloroquine Compared With Methotrexate

“…We did not assess for concomitant malignancy, so it is possible this could be a confounding variable causing increased hospitalization or cutaneous reactions from cancer or response to cancer therapy. An additional limitation is that although there is validation for the use of some ICD codes for drug eruptions ( 16 , 17 ) to enhance confidence in diagnostic accuracy, there was no way to specifically determine that the rash was caused by the medication; rashes may thus reflect ongoing disease activity from DM in some cases ( 5 , 9 ). Future directions could include further patient subtyping, such as paraneoplastic DM, and comparing patients on other medications, such as HCQ new users to azathioprine or mycophenolate new users.…”

Response to ‘Validation of generalized drug‐related rash diagnoses using International Classification of Diseases 9th and 10th Revision codes’

“…However, the authors did not mention the negative predictive value (NPV) of the case identification, which evaluates how many cases identified as not being drug-related rashes are truly not drug-related rashes. In a health database, classification and coding of a patient might be inaccurate due to over-or undercoding, 2 and therefore not all cases can be correctly identified by ICD codes. Hence, we suggest that the authors should evaluate both PPV and NPV for the disease validation.…”