diff --git a/DESCRIPTION b/DESCRIPTION
index d00f17dd..62adc0ee 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -34,7 +34,7 @@ Imports:
     readr,
     rlang,
     stringr,
-    susieR,
+    susieR (>= 0.16.2),
     tibble,
     tictoc,
     tidyr,
diff --git a/NAMESPACE b/NAMESPACE
index 225f15c6..5d0c6e38 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -373,6 +373,7 @@ importFrom(susieR,mr.ash.rss)
 importFrom(susieR,susie)
 importFrom(susieR,susie_get_cs)
 importFrom(susieR,susie_rss)
+importFrom(susieR,susie_ser)
 importFrom(susieR,univariate_regression)
 importFrom(tibble,as_tibble)
 importFrom(tibble,tibble)
diff --git a/R/file_utils.R b/R/file_utils.R
index dc6c7f1b..24807af8 100644
--- a/R/file_utils.R
+++ b/R/file_utils.R
@@ -1396,9 +1396,15 @@ load_rss_data <- function(sumstat_path, column_file_path = NULL, n_sample = 0, n
   sumstats <- load_tsv_region(file_path = sumstat_path, region = region, extract_region_name = extract_region_name, region_name_col = region_name_col)
 
   # To keep a log message
-  n_variants <- nrow(sumstats)
+  n_variants <- if (is.null(sumstats)) 0L else nrow(sumstats)
+  if (length(n_variants) == 0 || is.na(n_variants)) {
+    n_variants <- 0L
+  }
   if (n_variants == 0) {
     message(paste0("No variants in region ", region, "."))
+    if (is.null(sumstats)) {
+      sumstats <- data.frame()
+    }
     return(list(sumstats = sumstats, n = NULL, var_y = NULL))
   } else {
     message(paste0("Region ", region, " include ", n_variants, " in input sumstats."))
diff --git a/R/sumstats_qc.R b/R/sumstats_qc.R
index 16e59b95..d0f13b6a 100644
--- a/R/sumstats_qc.R
+++ b/R/sumstats_qc.R
@@ -210,8 +210,8 @@ ld_mismatch_qc <- function(zScore, R = NULL, X = NULL, nSample = NULL,
 #'
 #'   When the combined path receives genotype-backed reference data
 #'   (\code{X_ref}), basic harmonization avoids constructing an LD matrix. PIP
-#'   screening uses an LD-independent single-effect screen with
-#'   \code{susie_rss(R = diag(p), L = 1, max_iter = 1)}, and LD-mismatch QC
+#'   screening uses the LD-independent single-effect summary-statistic model
+#'   \code{susie_ser(coverage = NULL)}, and LD-mismatch QC
 #'   computes only the filtered local correlation matrix required by
 #'   SLALOM/DENTIST. RAISS imputation temporarily centers/scales
 #'   genotype-backed \code{X_ref} before using the whole-region genotype/SVD
@@ -228,6 +228,7 @@ ld_mismatch_qc <- function(zScore, R = NULL, X = NULL, nSample = NULL,
 #'                                qc_method = "none")
 #'
 #' @importFrom dplyr mutate row_number filter pull
+#' @importFrom susieR susie_ser
 #' @export
 summary_stats_qc <- function(sumstats, LD_data, n = NULL,
                              method = c("slalom", "dentist"),
@@ -517,9 +518,7 @@ summary_stats_qc <- function(sumstats, LD_data, n = NULL,
     if (cutoff < 0) cutoff <- 3 / nrow(sumstats)
     message("QC track: running LD-independent single-effect initial screen for summary-stat study ",
             study, ".")
-    pip_args <- list(z = sumstats$z, R = diag(nrow(sumstats)),
-                     L = 1, max_iter = 1, n = n)
-    pip <- do.call(susie_rss, pip_args)$pip
+    pip <- susie_ser(z = sumstats$z, n = n, coverage = NULL)$pip
     if (!any(pip > cutoff)) {
       message("Skipping follow-up analysis: No signals above PIP threshold ", cutoff)
       message("QC track: skipping summary-stat study ", study,
diff --git a/man/summary_stats_qc.Rd b/man/summary_stats_qc.Rd
index 541310e0..bf267c9c 100644
--- a/man/summary_stats_qc.Rd
+++ b/man/summary_stats_qc.Rd
@@ -77,8 +77,8 @@ This function applies the specified quality control method to the
 
   When the combined path receives genotype-backed reference data
   (\code{X_ref}), basic harmonization avoids constructing an LD matrix. PIP
-  screening uses an LD-independent single-effect screen with
-  \code{susie_rss(R = diag(p), L = 1, max_iter = 1)}, and LD-mismatch QC
+  screening uses the LD-independent single-effect summary-statistic model
+  \code{susie_ser(coverage = NULL)}, and LD-mismatch QC
   computes only the filtered local correlation matrix required by
   SLALOM/DENTIST. RAISS imputation temporarily centers/scales
   genotype-backed \code{X_ref} before using the whole-region genotype/SVD
diff --git a/tests/testthat/test_file_utils.R b/tests/testthat/test_file_utils.R
index c3c985dc..0dfd8749 100644
--- a/tests/testthat/test_file_utils.R
+++ b/tests/testthat/test_file_utils.R
@@ -1435,6 +1435,25 @@ test_that("load_rss_data returns empty sumstats message for zero-row region", {
   file.remove(tmp_sumstat, tmp_col)
 })
 
+test_that("load_rss_data handles tabix regions with no records", {
+  tmp_sumstat <- tempfile(fileext = ".tsv")
+  writeLines("chrom\tpos\tb\ts", tmp_sumstat)
+  tmp_col <- tempfile(fileext = ".txt")
+  writeLines(c("beta:b", "se:s"), tmp_col)
+
+  local_mocked_bindings(
+    load_tsv_region = function(...) NULL
+  )
+  expect_message(
+    result <- suppressWarnings(load_rss_data(tmp_sumstat, tmp_col, region = "chr21:1-2")),
+    "No variants in region chr21:1-2."
+  )
+  expect_true(is.data.frame(result$sumstats))
+  expect_equal(nrow(result$sumstats), 0)
+  expect_null(result$n)
+  file.remove(tmp_sumstat, tmp_col)
+})
+
 test_that("load_rss_data extracts n from n_sample column in sumstats", {
   tmp_sumstat <- tempfile(fileext = ".tsv")
   df <- data.frame(
diff --git a/tests/testthat/test_sumstats_qc.R b/tests/testthat/test_sumstats_qc.R
index a7152f42..68322daa 100644
--- a/tests/testthat/test_sumstats_qc.R
+++ b/tests/testthat/test_sumstats_qc.R
@@ -435,9 +435,9 @@ test_that("summary_stats_qc PIP screening uses LD-independent SER", {
 
   local_mocked_bindings(
     compute_LD = function(...) stop("compute_LD should not be called"),
-    susie_rss = function(z, R = NULL, X = NULL, ...) {
-      expect_null(X)
-      expect_equal(R, diag(length(z)))
+    susie_ser = function(z, n = NULL, coverage = 0.95, ...) {
+      expect_equal(n, rss_input$n)
+      expect_null(coverage)
       list(pip = rep(1, length(z)))
     }
   )
diff --git a/tests/testthat/test_univariate_pipeline.R b/tests/testthat/test_univariate_pipeline.R
index 20eaa7f1..762a22d3 100644
--- a/tests/testthat/test_univariate_pipeline.R
+++ b/tests/testthat/test_univariate_pipeline.R
@@ -947,7 +947,7 @@ test_that("rss: pip_cutoff_to_skip > 0, no signal => early return", {
   local_mocked_bindings(
     load_rss_data = function(...) list(sumstats = ss, n = 1000, var_y = 1),
     rss_basic_qc = function(...) list(sumstats = ss, LD_mat = ld_mat),
-    susie_rss = function(...) list(pip = rep(0.01, 5)),
+    susie_ser = function(...) list(pip = rep(0.01, 5)),
   )
 
   result <- expect_message(
@@ -1004,7 +1004,7 @@ test_that("rss: negative pip_cutoff_to_skip auto-computes threshold", {
   local_mocked_bindings(
     load_rss_data = function(...) list(sumstats = ss, n = 1000, var_y = 1),
     rss_basic_qc = function(...) list(sumstats = ss, LD_mat = ld_mat),
-    susie_rss = function(...) list(pip = rep(0.01, 5)),
+    susie_ser = function(...) list(pip = rep(0.01, 5)),
   )
 
   # auto threshold = 3 * 1/5 = 0.6, all PIPs are 0.01 so skip