Introduction
Prevalence quantifies the number of people known to be living with and beyond a diagnosis at a given point in time. Understanding the size of the population living with and beyond a diagnosis of a disease or congenital anomaly can support planning for the delivery of local health and social care services, quantify the ‘burden’ of disease or number of children living with a congenital anomaly in an area or population. Therefore this can help determine the number of people who may have unmet health needs that may benefit from new treatment interventions or support.
Prevalence is a product of both the incidence and survival and should be interpreted with these factors in mind, especially if making comparisons across different disease/condition types or populations. For example, a disease or condition with high incidence of new diagnoses but poor survival outcomes could have similar prevalence to a less common condition that has a high survival rate.
Observed vs. complete prevalence
There are different ways to measure prevalence depending on the data that are available.
Complete prevalence describes the total number of people ever diagnosed with a disease or congenital anomaly who are alive at a given point in time (the index date). Because registries do not cover a sufficiently long time period to have recorded all possible diagnoses, in practice, complete prevalence is usually estimated using statistical models.
Observed, limited duration prevalence counts those living with a disease or congenital anomaly whose diagnosis can be ‘observed’ in the data, i.e., a registration record exists for their diagnosis. Observed prevalence is also referred to as limited duration as it can only be calculated over the length of time available in the data source used. For example, in the National Cancer Registration Dataset (NCRD), observed, limited duration cancer prevalence can be calculated using cancer registrations as far back as 1995. For rare disease and congenital anomalies data is often limited to a finite range of years and the reported prevalence should be interpreted accordingly. National congenital anomaly registration began in 2018 and prevalence can be calculated in children born since this date.
Congenital anomaly point prevalence and birth prevalence
There are different methods used to calculate prevalence depending on the data available and the nature of the condition. Here, we present point prevalence for each condition; that is, the number of living people at a specific point in time that are reported to have been diagnosed with the condition. This is in contrast to birth prevalence, which is commonly used to describe congenital anomalies since these would be present at birth, whereas conditions such as cancer are most commonly acquired after birth. Point prevalence is a function of both birth prevalence and survival.
Cancer prevalence outputs
The National Disease Registration Service (NDRS) produces a dashboard and the associated data for observed, limited duration cancer prevalence in England at the most recent index date available in the National Cancer Registration data set.
Data are presented for all cancers combined and for a range of cancer types, broken down by patient demographics and by geographical area.
The dashboard presents prevalence counts and rates for Clinical Commissioning Groups, Sustainability and Transformation Partnerships and Cancer Alliances across England, broken down by population demographics and for different tumour types.
View the cancer prevalence dashboard and supporting information to find out more.
Rare conditions statistics output
From 2024 NDRS has been producing experimental point prevalence counts for selected rare diseases (including some rare cancers) and congenital anomalies. This is observed, limited duration prevalence at the most recent index date allowed by the data.
Data is presented as an overall prevalence rate for England without further breakdowns, due to the rare nature of the conditions.
Last edited: 9 June 2025 9:24 am
