Monogenic diabetes in New Zealand - An audit based revision of the monogenic diabetes genetic testing pathway in New Zealand.

Aims: To evaluate (a) the diagnostic yield of genetic testing for monogenic diabetes when using single gene and gene panel-based testing approaches in the New Zealand (NZ) population, (b) whether the MODY (Maturity Onset Diabetes of the Young) pre-test probability calculator can be used to guide referrals for testing in NZ, (c) the number of referrals for testing for Maori/Pacific ethnicities compared to NZ European, and (d) the volume of proband vs cascade tests being requested. Methods: A retrospective audit of 495 referrals, from NZ, for testing of monogenic diabetes genes was performed. Referrals sent to LabPlus (Auckland) laboratory for single gene testing or small multi-gene panel testing, or to the Exeter Genomics Laboratory, UK, for a large gene panel, received from January 2014 - December 2021 were included. Detection rates of single gene, small multi-gene and large gene panels (neonatal and non-neonatal), and cascade testing were analysed. Pre-test probability was calculated using the Exeter MODY probability calculator and ethnicity data was also collected. Results: The diagnostic detection rate varied across genes, from 32% in GCK, to 2% in HNF4A, with single gene or small gene panel testing averaging a 12% detection rate. Detection rate by type of panel was 9% for small gene panel, 23% for non-neonatal monogenic diabetes large gene panel and 40% for neonatal monogenic diabetes large gene panel. 45% (67/147) of patients aged 1-35 years at diabetes diagnosis scored <20% on MODY pre-test probability, of whom 3 had class 4/5 variants in HNF1A, HNF4A or HNF1B. Ethnicity data of those selected for genetic testing correlated with population diabetes prevalence for Maori (15% vs 16%), but Pacific People appeared under-represented (8% vs 14%). Only 1 in 6 probands generated a cascade test. Conclusions: A new monogenic diabetes testing algorithm for NZ is proposed, which directs clinicians to choose a large gene panel in patients without syndromic features who score a pre-test MODY probability of above 20%.

Genomic characterisation of diffuse large B-cell lymphoma.

Diffuse large B-cell lymphoma (DLBCL) is a genomically heterogenous disease comprised of many subtypes that display significantly different clinical outcomes, in the context of treatment with conventional immunochemotherapy. Poor clinical outcomes in some subtypes, and imperfect identification of high risk individuals in otherwise low risk subgroups, demonstrate there is room for improvement in the subclassification and risk stratification of DLBCL. In addition, more comprehensive profiling may lead to improved molecular testing guided treatment selection. Existing characterisation and risk stratification strategies, such as division of DLBCL into activated B-cell (ABC) and germinal centre B-cell (GCB) subtypes, although prognostically useful, may oversimplify the underlying biology and have proven to be less useful in improving therapy selection. Several groups have proposed more predictive molecular testing based prognostic models with potentially more relevance to therapy choice. These alternative approaches use more resource intensive comprehensive genomic profiling strategies which present practical challenges to implement in diagnostic laboratories. The addition of genomic testing to the subclassification of DLBCL shows promise, but laboratories must identify testing strategies relevant to clinical practice. A consensus on optimal molecular profiling techniques is yet to be achieved. In this article we review various next generation sequencing-based analytical techniques and molecular classification models proposed recently. Emerging therapeutics where molecular profiling may guide patient selection are also reviewed. The potential utility of genomic testing in DLBCL is discussed, in addition to practical considerations when considering introducing genomics into the diagnostic laboratory.

Type 2 diabetes presenting with hyperglycaemic hyperosmolar state in an adolescent renal transplant patient.

Hyperglycaemic hyperosmolar state (HHS) is a life-threatening condition rarely seen in paediatrics. It is becoming increasingly recognised with the growing incidence of childhood type 2 diabetes mellitus (T2DM). We present a 16-year-old boy with Bardet-Biedl syndrome, with comorbidities including chronic renal impairment requiring renal transplant, isolated growth hormone (GH) deficiency and obesity, who presented on routine follow-up with new onset T2DM and in HHS. Investigations revealed hyperglycaemia (45.7 mmol/L), ketones of 0.1 mmol/L, pH 7.38 and osmolarity 311 mOsmol/kg. After acute management with fluid resuscitation and intravenous insulin, he is now stable on metformin. He has lost weight, renal function is stable and he has stopped GH therapy. We discuss the dilemmas encountered in his long-term management due to his renal transplant and comorbidities, and whether or not, given his significant T2DM risk, this case was preventable or predictable.