Estimating the Size of the HCV Infection Prevalence: A Modeling Approach Using the Incidence of Cases Reported to an Official Notification System

Abstract

In this paper we propose two methods to give a first rough estimate of the actual number of hepatitis C virus (HCV)-infected individuals (prevalence) taking into account the notification rate of newly diagnosed infections (incidence of notification) and the size of the liver transplantation waiting list (LTWL) of patients with liver failure due to chronic HCV infection. Both approaches, when applied to the Brazilian HCV situation converge to the same results, that is, the methods proposed reproduce both the prevalence of reported cases and the LTWL with reasonable accuracy. We use two methods to calculate the prevalence of HCV that, as a first, and very crude approximation, assumes that the actual prevalence of HCV in Brazil is proportional to the reported incidence to the official notification system with a constant denoted [Formula: see text]. In the paper we discuss the limitations and advantages of this assumption. With the two methods we calculated [Formula: see text], which reproduces both the reported incidence and the size of the LTWL. With the value of [Formula: see text] we calculated the prevalence I(a) (the integral of which resulted in 1.6 million people living with the infection in Brazil, most of whom unidentified). Other variables related to HCV infection (e.g., the distribution of the proportion of people aged a who got infected n years ago) can be easily calculated from this model. These new variables can then be measured and the model can be recursively updated, improving its accuracy.

Estimating the prevalence of infectious diseases from under-reported age-dependent compulsorily notification databases

“…In that paper, we assumed a steady state for the period between 2004 and 2012, and we concluded that the non-notified to notified ratio in the number of infections was about 7 to 1. The current work is an extension of that paper and we relaxed the steady state The method demonstrated to be accurate in retrieving the number of infected individuals for the case of HCV and the results are in good accordance with the previous estimations by Amaku et al (2016).…”

“…This reported incidence was extrapolated backwards until 1932. It is therefore not surprising that the published number in Amaku et al (2016) including the third and fourth columns of Table 2…”

“…Both approaches, when applied to the Brazilian HCV situation converged to the same results, that is, the methods proposed reproduce both the prevalence of reported cases and the LTWL with reasonable accuracy. In that paper we show how to calculate the prevalence of people living with HCV in Brazil, which resulted in a value up to 8 times higher than the official reported number of cases [13] .…”

“…Assuming steady state, the system (1) was solved by Amaku et al [13] (2016) to calculate the prevalence of HCV in Brazil. The work that follows is an extension of the methods described there and its results are in accordance with the previous results for the cases where real data are available.…”

“…Recurrence (7) can be solved by well known methods and the prevalence of notified and non-notified individuals can be estimated (see equations (13) and (14) below).…”