diff --git a/vatools/vcf_expression_annotator.py b/vatools/vcf_expression_annotator.py
index 65d36e8..1818feb 100644
--- a/vatools/vcf_expression_annotator.py
+++ b/vatools/vcf_expression_annotator.py
@@ -54,7 +54,7 @@ def to_array(dictionary):
 
 def parse_expression_file(args, vcf_reader, vcf_writer):
     if args.format == 'stringtie' and args.mode == 'transcript':
-        df_all = read_gtf(args.expression_file)
+        df_all = read_gtf(args.expression_file, usecols=['reference_id', 'transcript_id', 'TPM', 'feature'])
         df = df_all[df_all["feature"] == "transcript"]
         id_column = resolve_stringtie_id_column(args, df.columns.values)
     else:
@@ -106,24 +106,23 @@ def create_vcf_writer(args, vcf_reader):
         output_file = args.output_vcf
     return vcfpy.Writer.from_path(output_file, new_header)
 
-def add_expressions(entry, is_multi_sample, sample_name, df, items, tag, id_column, expression_column, ignore_ensembl_id_version, missing_expressions_count, entry_count):
-    expressions = {}
-    for item in items:
-        entry_count += 1
-        if ignore_ensembl_id_version:
-            subset = df.loc[df['transcript_without_version'] == re.sub(r'\.[0-9]+$', '', item)]
-        else:
-            subset = df.loc[df[id_column] == item]
-        if len(subset) > 0:
-            expressions[item] = subset[expression_column].sum()
-        else:
-            missing_expressions_count += 1
+def add_expressions(entry, is_multi_sample, sample_name, df, items, tag, id_column, expression_column, ignore_ensembl_id_version, missing_expressions_count):
+    subset = None
+    if ignore_ensembl_id_version:
+        items_without_version = [re.sub(r'\.[0-9]+$', '', item) for item in items]
+        subset = df[df['transcript_without_version'].isin(items_without_version)]
+        for item in items:
+            subset.loc[subset['transcript_without_version'] == re.sub(r'\.[0-9]+$', "", item), id_column] = item
+    else:
+        subset = df[df[id_column].isin(items)]
+    expressions = subset[[id_column, expression_column]].groupby(id_column).sum().to_dict()[expression_column]
+    missing_expressions_count += (len(items) - len(expressions))
     if is_multi_sample:
         entry.FORMAT += [tag]
         entry.call_for_sample[sample_name].data[tag] = to_array(expressions)
     else:
         entry.add_format(tag, to_array(expressions))
-    return (entry, missing_expressions_count, entry_count)
+    return (entry, missing_expressions_count)
 
 def define_parser():
     parser = argparse.ArgumentParser(
@@ -216,11 +215,13 @@ def main(args_input = sys.argv[1:]):
         if args.mode == 'gene':
             genes = list(genes)
             if len(genes) > 0:
-                (entry, missing_expressions_count, entry_count) = add_expressions(entry, is_multi_sample, args.sample_name, df, genes, 'GX', id_column, expression_column, args.ignore_ensembl_id_version, missing_expressions_count, entry_count)
+                (entry, missing_expressions_count) = add_expressions(entry, is_multi_sample, args.sample_name, df, genes, 'GX', id_column, expression_column, args.ignore_ensembl_id_version, missing_expressions_count)
+                entry_count += len(genes)
         elif args.mode == 'transcript':
             transcript_ids = list(transcript_ids)
             if len(transcript_ids) > 0:
-                (entry, missing_expressions_count, entry_count) = add_expressions(entry, is_multi_sample, args.sample_name, df, transcript_ids, 'TX', id_column, expression_column, args.ignore_ensembl_id_version, missing_expressions_count, entry_count)
+                (entry, missing_expressions_count) = add_expressions(entry, is_multi_sample, args.sample_name, df, transcript_ids, 'TX', id_column, expression_column, args.ignore_ensembl_id_version, missing_expressions_count)
+                entry_count += len(transcript_ids)
         vcf_writer.write_record(entry)
 
     vcf_reader.close()