Which laboratory test is the best predictor of blood glucose control over the previous few months?

Choice A reason: Type 1 diabetes cannot be treated with oral glycemic agents. These medications are typically used to manage type 2 diabetes, which is characterized by insulin resistance rather than a lack of insulin production. In type 1 diabetes, the pancreas is unable to produce insulin due to an autoimmune destruction of insulin-producing beta cells. Therefore, individuals with type 1 diabetes require insulin therapy to manage their blood glucose levels effectively.

Choice B reason: Type 1 diabetes has a definite genetic component, though it is not solely determined by genetics. A combination of genetic predisposition and environmental factors, such as viral infections or other autoimmune triggers, can lead to the development of type 1 diabetes. Certain genes, including those in the HLA region, are known to increase susceptibility to the disease.

Choice C reason: In type 1 diabetes, the pancreas is indeed completely unable to produce insulin. This is due to an autoimmune attack on the beta cells of the pancreas, which are responsible for insulin production. Without insulin, the body cannot regulate blood glucose levels, leading to hyperglycemia and the need for exogenous insulin administration.

Choice D reason: Type 1 diabetes often has an acute onset, particularly in children and young adults. Symptoms can develop rapidly over a few days to weeks, including increased thirst, frequent urination, unintended weight loss, and severe fatigue. This acute presentation is a hallmark of the disease and contrasts with the more gradual onset seen in type 2 diabetes.

Choice A reason: Most patients with CNS tumors do not develop metastatic disease. Central nervous system (CNS) tumors, including brain tumors, typically do not metastasize outside the CNS. Instead, they grow and exert pressure on adjacent brain structures, leading to neurological symptoms.

Choice B reason: While brain tumors can be very deadly, the TNM classification system is not avoided due to the lethality of the tumors. The main reason for not using the TNM system is because the classification criteria do not align well with the unique aspects of brain tumors.

Choice C reason: Tumor size is less relevant than the location and histology for brain tumors. The location of the tumor within the brain and its histological characteristics (e.g., type, grade, and molecular features) are more critical for prognosis and treatment planning. Brain tumors can cause significant clinical issues even when small, depending on their location.

Choice D reason: Brain tumors can have a poor prognosis, but this is not the reason the TNM classification is not used. The classification system's limitation is primarily due to the fact that brain tumors' behavior and treatment considerations depend more on their location and histological features than on tumor size, nodal involvement, and metastasis, which are the focus of the TNM system.