INTRODUCTIONThis study aimed to describe the clinical presentation, treatment and outcome of patients with relapsing polychondritis (RP) who were seen at a large tertiary-care academic medical institution in Singapore.

METHODSThe medical records of all patients diagnosed with RP at the Department of Rheumatology and Immunology, Singapore General Hospital, Singapore, between 2005 and 2013 were reviewed. The diagnosis of RP was made using the modified McAdam criteria.

RESULTSTen patients were diagnosed with RP during the study period. Among these patients, five fulfilled the modified McAdam criteria and five were probable cases of RP. The most common clinical presentations were auricular chondritis (n = 9), episcleritis or scleritis (n = 5), and large airway involvement (n = 3). All of the patients received prednisolone. Five patients developed haematological disorders. Patients with both RP and haematological disorders had a longer duration of RP symptoms prior to diagnosis, compared to patients with RP who did not develop haematological disorders (average duration of symptoms 14.7 months vs. 4.2 months).

CONCLUSIONThe high frequency of patients with haematological malignancies in this series was unexpected. Myelodysplastic syndrome has been reported, but other haematological malignancies are rarely associated with RP. As the association between haematological malignancies and RP is currently unclear, the threshold for haematological/lymphoproliferative screening should be lowered in patients with RP.

Functional reference limits describe key changes in the physiological relationship between a pair of physiologically related components. Statistically, this can be represented by a significant change in the curvature of a mathematical function or curve (e.g., an observed plateau). The point at which the statistical relationship changes significantly is the point of curvature inflection and can be mathematically modeled from the relationship between the interrelated biomarkers. Conceptually, they reside between reference intervals, which describe the statistical boundaries of a single biomarker within the reference population, and clinical decision limits that are often linked to the risk of morbidity or mortality and set as thresholds. Functional reference limits provide important physiological and pathophysiological insights that can aid laboratory result interpretation. Laboratory professionals are in a unique position to harness data from laboratory information systems to derive clinically relevant values. Increasing research on and reporting of functional reference limits in the literature will enhance their contribution to laboratory medicine and widen the evidence base used in clinical decision limits, which are currently almost exclusively contributed to by clinical trials. Their inclusion in laboratory reports will enhance the intellectual value of laboratory professionals in clinical care beyond the statistical boundaries of a healthy reference population and pave the way to them being considered in shaping clinical decision limits. This review provides an overview of the concepts related to functional reference limits, clinical examples of their use, and the impetus to include them in laboratory reports.