diff --git a/R/parameters.R b/R/parameters.R
index 4804420c..bfef758f 100644
--- a/R/parameters.R
+++ b/R/parameters.R
@@ -1,66 +1,9 @@
-#' Read right-truncation PMF into memory
-#'
-read_right_truncation_pmf <- function(path,
-                                      disease = c(
-                                        "COVID-19",
-                                        "Influenza",
-                                        "test"
-                                      ),
-                                      as_of_date,
-                                      state) {
-  rlang::arg_match(disease)
-  check_path(path)
-
-  # The comparison fails if the dates are not in string format, reformat if
-  # needed
-  if (inherits(as_of_date, "Date")) {
-    as_of_date <- format(as_of_date, "%Y-%m-%d")
-  }
-
-  con <- DBI::dbConnect(duckdb::duckdb())
-  pmf_df <- rlang::try_fetch(
-    DBI::dbGetQuery(
-      conn = con,
-      statement = "
-    SELECT value
-    FROM read_parquet(?)
-    WHERE 1=1
-      AND parameter = 'right_truncation'
-      AND disease = ?
-      AND start_date < ? :: DATE
-      AND (end_date > ? OR end_date IS NULL)
-      AND geo_value = ?
-      ;
-         ",
-      params = list(
-        path,
-        disease,
-        as_of_date,
-        as_of_date,
-        state
-      )
-    ),
-    error = function(cnd) {
-      cli::cli_abort(c(
-        "Failure loading {.arg right_truncation} from {.path {path}}",
-        "Using {.val {disease}} and {.val {as_of_date}}",
-        "Original error: {cnd}"
-      ))
-    }
-  )
-  DBI::dbDisconnect(con)
-
-  pmf <- check_returned_pmf(pmf_df)
-  cli::cli_alert_success("{.arg right_truncation} loaded")
-
-  return(pmf)
-}
-
-#' Read generation and delay interval PMFs into memory
+#' Read parameter PMFs into memory
 #'
 #' Using DuckDB from a parquet file. The function expects the file to be in SCD2
 #' format with column names:
 #' * parameter
+#' * geo_value
 #' * disease
 #' * start_date
 #' * end_date
@@ -69,21 +12,23 @@ read_right_truncation_pmf <- function(path,
 #' @param path A path to a local file
 #' @param disease One of "COVID-19" or "Influenza"
 #' @param as_of_date The parameters "as of" the date of the model run
-#' @param parameter One of "generation interval" or "delay"
+#' @param parameter One of "generation interval", "delay", or "right-truncation
 #'
 #' @return A PMF vector
 #' @export
 read_interval_pmf <- function(path,
                               disease = c("COVID-19", "Influenza", "test"),
                               as_of_date,
-                              parameter = c("generation_interval", "delay")) {
+                              parameter = c(
+                                "generation_interval",
+                                "delay",
+                                "right_truncation"
+                              ),
+                              state = NA) {
   rlang::arg_match(parameter)
   rlang::arg_match(disease)
 
-  cli::cli_alert_info("Reading {.arg {parameter}} from {.path {path}}")
-  if (!file.exists(path)) {
-    cli::cli_abort("File {.path {path}} does not exist")
-  }
+  check_path(path)
 
   # The comparison fails if the dates are not in string format, reformat if
   # needed
@@ -91,11 +36,9 @@ read_interval_pmf <- function(path,
     as_of_date <- format(as_of_date, "%Y-%m-%d")
   }
 
-  con <- DBI::dbConnect(duckdb::duckdb())
-  pmf_df <- rlang::try_fetch(
-    DBI::dbGetQuery(
-      conn = con,
-      statement = "
+  # Can't use `=` for NULL comparison and dbBind can't insert a ? after an is
+  if (rlang::is_na(state) || rlang::is_null(state)) {
+    query <- "
     SELECT value
     FROM read_parquet(?)
     WHERE 1=1
@@ -103,20 +46,50 @@ read_interval_pmf <- function(path,
       AND disease = ?
       AND start_date < ? :: DATE
       AND (end_date > ? OR end_date IS NULL)
-      ;
-         ",
-      params = list(
-        path,
-        parameter,
-        disease,
-        as_of_date,
-        as_of_date
-      )
+      AND geo_value IS NULL
+    ;
+    "
+    parameters <- list(
+      path,
+      parameter,
+      disease,
+      as_of_date,
+      as_of_date
+    )
+  } else {
+    query <- "
+    SELECT value
+    FROM read_parquet(?)
+    WHERE 1=1
+      AND parameter = ?
+      AND disease = ?
+      AND start_date < ? :: DATE
+      AND (end_date > ? OR end_date IS NULL)
+      AND geo_value = ?
+    ;
+    "
+
+    parameters <- list(
+      path,
+      parameter,
+      disease,
+      as_of_date,
+      as_of_date,
+      state
+    )
+  }
+
+  con <- DBI::dbConnect(duckdb::duckdb())
+  pmf_df <- rlang::try_fetch(
+    DBI::dbGetQuery(
+      conn = con,
+      statement = query,
+      params = parameters
     ),
     error = function(cnd) {
       cli::cli_abort(c(
         "Failure loading {.arg {parameter}} from {.path {path}}",
-        "Using {.val {disease}} and {.val {as_of_date}}",
+        "Using {.val {disease}}, {.val {as_of_date}}, and {.val {state}}",
         "Original error: {cnd}"
       ))
     }
diff --git a/tests/testthat/test-parameters.R b/tests/testthat/test-parameters.R
index 01a1677d..b7c77577 100644
--- a/tests/testthat/test-parameters.R
+++ b/tests/testthat/test-parameters.R
@@ -17,8 +17,9 @@ test_that("Can read right-truncation on happy path", {
       start_date = start_date,
       end_date = NA
     )
-    actual <- read_right_truncation_pmf(
+    actual <- read_interval_pmf(
       path = path,
+      parameter = parameter,
       disease = disease,
       as_of_date = start_date + 1,
       state = "test"
@@ -40,8 +41,9 @@ test_that("Can read right-truncation on happy path", {
       start_date = start_date,
       end_date = NA
     )
-    actual <- read_right_truncation_pmf(
+    actual <- read_interval_pmf(
       path = path,
+      parameter = parameter,
       disease = disease,
       as_of_date = start_date + 1,
       state = "test"
@@ -50,6 +52,34 @@ test_that("Can read right-truncation on happy path", {
   expect_equal(actual, expected)
 })
 
+test_that("Invalid PMF errors", {
+  expected <- c(0.8, -0.1)
+  path <- "test.parquet"
+  parameter <- "right_truncation"
+  start_date <- as.Date("2023-01-01")
+
+  # COVID-19
+  disease <- "COVID-19"
+  withr::with_tempdir({
+    write_sample_parameters_file(
+      value = expected,
+      path = path,
+      state = "test",
+      disease = disease,
+      parameter = parameter,
+      param = parameter,
+      start_date = start_date,
+      end_date = NA
+    )
+    expect_error(read_interval_pmf(
+      path = path,
+      parameter = parameter,
+      disease = disease,
+      as_of_date = start_date + 1,
+      state = "test"
+    ))
+  })
+})
 
 
 test_that("Can read delay on happy path", {
@@ -64,7 +94,7 @@ test_that("Can read delay on happy path", {
     write_sample_parameters_file(
       value = expected,
       path = path,
-      state = "test",
+      state = NA,
       disease = disease,
       parameter = parameter,
       param = parameter,
@@ -87,7 +117,7 @@ test_that("Can read delay on happy path", {
     write_sample_parameters_file(
       value = expected,
       path = path,
-      state = "test",
+      state = NA,
       disease = disease,
       parameter = parameter,
       param = parameter,