Biology • Year 12 • Module 8 • Lesson 14
Treating One Non-infectious Disease: Type 2 Diabetes
Develop HSC Band 5–6 extended-response technique, synthesising disease mechanism, trial data, sustainability and equity into a justified judgement about treatment and future research directions.
1. Data-driven evaluation, choosing a management pathway (Band 5–6)
Stimulus. A regional health service reviews twelve-month outcomes for 300 adults newly diagnosed with Type 2 diabetes, allocated to three management pathways.
| Pathway | Mean HbA1c fall | Reached target | Still on plan at 12 months | Annual cost per person |
|---|---|---|---|---|
| A, structured lifestyle program with dietitian support | 1.6% | 44% | 52% | $1,100 |
| B, metformin plus brief lifestyle advice | 1.3% | 51% | 86% | $180 |
| C, structured lifestyle program plus metformin | 2.1% | 68% | 74% | $1,260 |
Evaluate which pathway the health service should adopt as its default for newly diagnosed patients. In your answer you must: explain how each pathway acts on the disease mechanism; use the data to compare effectiveness; identify what the "still on plan" column reveals that the HbA1c column does not; and reach a justified judgement that considers cost and equity of access. 8 marks
2. Source critique, evaluate this media claim (Band 5–6)
"THE END OF DIABETES. A revolutionary new weekly injection has been shown to cause 17% body weight loss in trials, meaning Type 2 diabetes can now simply be cured. Doctors who still prescribe old-fashioned metformin tablets are failing their patients. Meanwhile, gene editing has already been approved as a medicine, so within a few years a single treatment will correct the genes that cause diabetes for good."
Source: adapted from an online health article, author and funding not stated.
Evaluate the scientific accuracy of this article. Identify at least four specific claims that are wrong, overstated or misleading, correct each one using lesson biology, and finish with a judgement about how the article should be used as a source. 8 marks
Q1, Marking guidelines, data-driven evaluation (8 marks)
Mechanism (2 marks). 1 mark for explaining that structured lifestyle programs act on insulin resistance itself, by increasing activity and reducing excess visceral fat so insulin receptor signalling improves, with exercise also raising insulin-independent GLUT4 uptake. 1 mark for explaining that metformin reduces hepatic glucose output and improves tissue insulin sensitivity, lowering glucose without forcing strained beta cells to secrete more insulin.
Data comparison (2 marks). 1 mark for identifying that Pathway C produces both the largest mean HbA1c fall (2.1%) and the highest proportion reaching target (68%), consistent with two complementary mechanisms acting together. 1 mark for noting the apparent inconsistency in Pathway A, which achieves a larger mean fall (1.6%) than B (1.3%) yet a lower proportion reaching target (44% versus 51%), indicating a wide spread of responses in A: some patients do very well and others not at all.
Retention column (2 marks). 1 mark for identifying that "still on plan at 12 months" measures sustainability, which a mean HbA1c cannot show. 1 mark for reasoning that Pathway A's 52% retention means nearly half discontinued, so its headline result is produced by a self-selected group who could sustain it, while B's 86% retention shows a plan most people can actually keep to. A biologically effective plan that is not sustained does not control glucose.
Judgement with cost and equity (2 marks). 1 mark for a clear, data-referenced recommendation. 1 mark for weighing cost and access honestly. Credit either defensible position: (i) adopt C as default because it is the most effective on both measures and the added cost over A is small, while noting that at $1,260 per person it may be unaffordable at scale and its 74% retention still leaves a quarter unsupported; or (ii) adopt B as the default because at $180 it costs roughly one seventh of C, retains the most patients and still gets 51% to target, reserving C for those not reaching target, which is a form of escalation. Full marks require the answer to name equity explicitly: a pathway available only to those who can afford it, take time off work or reach a dietitian will not reduce disease across the whole population.
Band guidance. Band 6 answers integrate mechanism, data and sustainability into one line of argument and qualify the recommendation. Band 4 answers describe the table without explaining mechanism or without reaching a judgement.
Q2, Marking guidelines, source critique (8 marks)
Award 1 mark for each error correctly identified and 1 mark for each accurate correction, to a maximum of 6, plus up to 2 marks for the judgement. Expected errors include:
- "Can now simply be cured." Type 2 diabetes can enter remission, meaning glucose returns to the non-diabetic range without medication, but this is not a cure: the genetic predisposition remains and weight regain brings recurrence.
- "17% body weight loss ... meaning diabetes is cured." Weight loss is a mechanism that improves insulin sensitivity, not an outcome measure of disease status. The relevant evidence would be glucose control and remission rates, and trial efficacy commonly shrinks to lower real-world effectiveness once adherence, cost and access intervene.
- "Doctors prescribing metformin are failing patients." Metformin remains an effective, low-cost, subsidised first-line medicine that reduces hepatic glucose output and improves insulin sensitivity. Choice of therapy must weigh effectiveness, side effects, cost, access and patient circumstances, not novelty. An unaffordable or unsubsidised injection may be the worse real-world choice.
- "Gene editing approved, so diabetes genes corrected within a few years." Casgevy, approved in 2023, is a somatic ex vivo therapy for sickle cell disease and beta-thalassaemia, both single-gene disorders of blood stem cells. Type 2 diabetes is multifactorial, with many variants each contributing small risk plus a large environmental contribution, so there is no single gene to correct.
- Source quality. Author, funding and any conflict of interest are not stated, no study is cited and no sample size or comparison group is given.
Judgement (2 marks). The article should not be used as evidence. It contains a real finding, the substantial weight loss seen with GLP-1 receptor agonists, wrapped in unsupported conclusions. It could be used only as a prompt to trace the underlying trial and check its design, population, effect size and funding. Full marks require the student to separate the defensible core claim from the overstatement rather than dismissing the article wholesale.