Nail ultrasonography for psoriatic arthritis and psoriasis patients: a systematic literature review

To systematically review the role of ultrasound (US) in the assessment of the joint-enthesial-nail apparatus in patients with psoriatic arthritis (PsA) or psoriasis (PSO) in terms of prevalence, diagnosis, prognosis, monitoring and treatment. A systematic literature review was conducted through medical databases (PubMed, Embase) and the grey literature up to February 2018. The main areas of application of nail US were first identified, allowing the development of research questions, which were rephrased following the PICOs methodology to develop inclusion criteria. Of the 585 studies produced by PubMed and Embase searches, 17 studies met the criteria for inclusion. Five additional studies were included: 1 from the hand search and 4 from the 2016-2017 ACR and EULAR congresses. The prevalence of nail plate changes varied from < 10 to 97%, for power Doppler signal from 20-30 to 96% and distal interphalangeal joint (DIJ) involvement from 8.9 to 100%. The performance of US nail/DIJ abnormalities in the diagnosis of PsA and PSO elementary lesions was analysed by five studies, with a wide heterogeneity. Reproducibility and reliability of US nil/DIJ were assessed by interclass correlation coefficient or Cohen's k and their values ranged from 0.6 to 0.9. The value of US nail/DIJ in the monitoring of the lesions was analysed only by a single study. The analysis revealed applications for US nail/DIJ in PsA and PSO and highlights limitations. Validation is strongly needed to demonstrate its appropriateness in the clinical practice and to define its diagnostic and prognostic role.