diff --git a/src/CodeService.js b/src/CodeService.js
index 917e291..4db29a3 100644
--- a/src/CodeService.js
+++ b/src/CodeService.js
@@ -77,7 +77,8 @@ class CodeService {
   async ensureValueSetsWithAPIKey(
     valueSetList = [],
     umlsAPIKey = env['UMLS_API_KEY'],
-    caching = true
+    caching = true,
+    options = { svsCodeSystemType: 'url' }
   ) {
     // First, filter out the value sets we already have
     const filteredVSList = valueSetList.filter(vs => {
@@ -112,7 +113,7 @@ class CodeService {
         // Catch errors and convert to resolutions returning an error.  This ensures Promise.all waits for all promises.
         // See: http://stackoverflow.com/questions/31424561/wait-until-all-es6-promises-complete-even-rejected-promises
         return this.api
-          .downloadValueSet(umlsAPIKey, oid, version, output, this.valueSets, caching)
+          .downloadValueSet(umlsAPIKey, oid, version, output, this.valueSets, caching, options)
           .catch(err => {
             debug(
               `Error downloading valueset ${oid}${version != null ? ` version ${version}` : ''}`,
@@ -151,10 +152,11 @@ class CodeService {
     library,
     checkIncluded = true,
     umlsAPIKey = env['UMLS_API_KEY'],
-    caching = true
+    caching = true,
+    options = { svsCodeSystemType: 'url' }
   ) {
     const valueSets = extractSetOfValueSetsFromLibrary(library, checkIncluded);
-    return this.ensureValueSetsWithAPIKey(Array.from(valueSets), umlsAPIKey, caching);
+    return this.ensureValueSetsWithAPIKey(Array.from(valueSets), umlsAPIKey, caching, options);
   }
 
   /**
diff --git a/src/fhir.js b/src/fhir.js
index fb87b5c..f6ee937 100644
--- a/src/fhir.js
+++ b/src/fhir.js
@@ -4,7 +4,17 @@ const fetch = require('node-fetch');
 const debug = require('debug')('vsac'); // To turn on DEBUG: $ export DEBUG=vsac
 const { Code, ValueSet } = require('cql-execution');
 
-async function downloadValueSet(apiKey, oid, version, output, vsDB = {}, caching = true) {
+async function downloadValueSet(
+  apiKey,
+  oid,
+  version,
+  output,
+  vsDB = {},
+  caching = true,
+  options = {
+    /* reserved for future use */
+  }
+) {
   const pages = await getValueSetPages(apiKey, oid, version);
   if (pages == null || pages.length === 0) {
     return;
diff --git a/src/svs.js b/src/svs.js
index 2b90541..1e630e7 100644
--- a/src/svs.js
+++ b/src/svs.js
@@ -6,26 +6,34 @@ const debug = require('debug')('vsac'); // To turn on DEBUG: $ export DEBUG=vsac
 const { Code, ValueSet } = require('cql-execution');
 const vsacCS = require('./vsac-code-systems');
 
-async function downloadValueSet(apiKey, oid, version, output, vsDB = {}, caching = true) {
+async function downloadValueSet(
+  apiKey,
+  oid,
+  version,
+  output,
+  vsDB = {},
+  caching = true,
+  options = { svsCodeSystemType: 'url' }
+) {
   debug(`Getting ValueSet: ${oid}${version != null ? ` version ${version}` : ''}`);
   const params = new URLSearchParams({ id: oid });
   if (version != null) {
     params.append('version', version);
   }
-  const options = {
+  const requestOptions = {
     headers: {
       Authorization: `Basic ${Buffer.from(`apikey:${apiKey}`).toString('base64')}`
     }
   };
   const response = await fetch(
     `https://vsac.nlm.nih.gov/vsac/svs/RetrieveValueSet?${params}`,
-    options
+    requestOptions
   );
   if (!response.ok) {
     throw new Error(response.status);
   }
   const data = await response.text();
-  parseVSACXML(data, vsDB);
+  parseVSACXML(data, vsDB, options);
   if (caching) {
     const file = path.join(output, `${oid}.xml`);
     await fs.writeFile(file, data);
@@ -33,10 +41,21 @@ async function downloadValueSet(apiKey, oid, version, output, vsDB = {}, caching
   }
 }
 
+function getVSACCodeSystem(codeSystems, system) {
+  if (
+    typeof codeSystems[system] !== 'undefined' &&
+    typeof codeSystems[system].uri !== 'undefined'
+  ) {
+    return codeSystems[system];
+  }
+
+  return null;
+}
+
 // Take in a string containing a string of the XML response from a VSAC SVS
 // response and parse it into a vsDB object.  This code makes strong
 // assumptions about the structure of the message.  See code below.
-function parseVSACXML(xmlString, vsDB = {}) {
+function parseVSACXML(xmlString, vsDB = {}, options = { svsCodeSystemType: 'url' }) {
   if (typeof xmlString === 'undefined' || xmlString == null || xmlString.trim().length == 0) {
     return;
   }
@@ -59,16 +78,31 @@ function parseVSACXML(xmlString, vsDB = {}) {
   // Loop over the codes and build the JSON.
   const codeList = [];
   for (let concept in conceptList) {
-    let system;
-    const systemOID = conceptList[concept]['$']['codeSystem'];
-    if (typeof vsacCS[systemOID] !== 'undefined' && typeof vsacCS[systemOID].uri !== 'undefined') {
-      system = vsacCS[systemOID].uri;
+    let system = conceptList[concept]['$']['codeSystem'];
+    const code = conceptList[concept]['$']['code'];
+    const version = conceptList[concept]['$']['codeSystemVersion'];
+    const systemOid = `urn:oid:${system}`;
+    const systemUri = getVSACCodeSystem(vsacCS, system);
+
+    if (options.svsCodeSystemType === 'oid') {
+      // Keep the oid system as is
+      system = systemOid;
+    } else if (options.svsCodeSystemType === 'both') {
+      // Optionally include both if they exist
+      if (systemUri !== null) {
+        codeList.push({ code, system: systemUri.uri, version });
+      }
+      // Include the standard oid system
+      system = systemOid;
     } else {
-      system = `urn:oid:${systemOID}`;
+      // Replace oid system with the url system, if one exists
+      if (systemUri !== null) {
+        system = systemUri.uri;
+      } else {
+        system = systemOid;
+      }
     }
 
-    const code = conceptList[concept]['$']['code'];
-    const version = conceptList[concept]['$']['codeSystemVersion'];
     codeList.push({ code, system, version });
   }
 
diff --git a/test/fixtures/2.16.840.1.113883.3.526.3.1032-oid-uri-vsdb.json b/test/fixtures/2.16.840.1.113883.3.526.3.1032-oid-uri-vsdb.json
new file mode 100644
index 0000000..1da919b
--- /dev/null
+++ b/test/fixtures/2.16.840.1.113883.3.526.3.1032-oid-uri-vsdb.json
@@ -0,0 +1,20 @@
+{
+  "2.16.840.1.113883.3.526.3.1032": {
+    "20170504": {
+      "oid": "2.16.840.1.113883.3.526.3.1032",
+      "version": "20170504",
+      "codes": [
+        {
+          "code": "8480-6",
+          "system": "http://loinc.org",
+          "version": "2.74"
+        },
+        {
+          "code": "8480-6",
+          "system": "urn:oid:2.16.840.1.113883.6.1",
+          "version": "2.74"
+        }
+      ]
+    }
+  }
+}
\ No newline at end of file
diff --git a/test/fixtures/2.16.840.1.113883.3.526.3.1032-oid-vsdb.json b/test/fixtures/2.16.840.1.113883.3.526.3.1032-oid-vsdb.json
new file mode 100644
index 0000000..59a3833
--- /dev/null
+++ b/test/fixtures/2.16.840.1.113883.3.526.3.1032-oid-vsdb.json
@@ -0,0 +1,15 @@
+{
+  "2.16.840.1.113883.3.526.3.1032": {
+    "20170504": {
+      "oid": "2.16.840.1.113883.3.526.3.1032",
+      "version": "20170504",
+      "codes": [
+        {
+          "code": "8480-6",
+          "system": "urn:oid:2.16.840.1.113883.6.1",
+          "version": "2.74"
+        }
+      ]
+    }
+  }
+}
\ No newline at end of file
diff --git a/test/fixtures/2.16.840.1.113883.3.600.2390-oid-uri-vsdb.json b/test/fixtures/2.16.840.1.113883.3.600.2390-oid-uri-vsdb.json
new file mode 100644
index 0000000..33cc1da
--- /dev/null
+++ b/test/fixtures/2.16.840.1.113883.3.600.2390-oid-uri-vsdb.json
@@ -0,0 +1,295 @@
+{
+  "2.16.840.1.113883.3.600.2390": {
+    "20210304": {
+      "oid": "2.16.840.1.113883.3.600.2390",
+      "version": "20210304",
+      "codes": [
+        {
+          "code": "160603005",
+          "system": "http://snomed.info/sct",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "160603005",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "160604004",
+          "system": "http://snomed.info/sct",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "160604004",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+
+
+        {
+          "code": "160605003",
+          "system": "http://snomed.info/sct",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "160605003",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+
+        {
+          "code": "160606002",
+          "system": "http://snomed.info/sct",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "160606002",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+
+        {
+          "code": "160619003",
+          "system": "http://snomed.info/sct",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "160619003",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+
+        {
+          "code": "230059006",
+          "system": "http://snomed.info/sct",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "230059006",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+
+        {
+          "code": "230060001",
+          "system": "http://snomed.info/sct",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "230060001",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+
+        {
+          "code": "230062009",
+          "system": "http://snomed.info/sct",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "230062009",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+
+        {
+          "code": "230063004",
+          "system": "http://snomed.info/sct",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "230063004",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+
+        {
+          "code": "230064005",
+          "system": "http://snomed.info/sct",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "230064005",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+
+        {
+          "code": "230065006",
+          "system": "http://snomed.info/sct",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "230065006",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+
+        {
+          "code": "266920004",
+          "system": "http://snomed.info/sct",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "266920004",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+
+        {
+          "code": "365981007",
+          "system": "http://snomed.info/sct",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "365981007",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+
+        {
+          "code": "365982000",
+          "system": "http://snomed.info/sct",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "365982000",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+
+        {
+          "code": "428041000124106",
+          "system": "http://snomed.info/sct",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "428041000124106",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+
+        {
+          "code": "428061000124105",
+          "system": "http://snomed.info/sct",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "428061000124105",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+
+        {
+          "code": "428071000124103",
+          "system": "http://snomed.info/sct",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "428071000124103",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+
+        {
+          "code": "449868002",
+          "system": "http://snomed.info/sct",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "449868002",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+
+        {
+          "code": "450811000124104",
+          "system": "http://snomed.info/sct",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "450811000124104",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+
+        {
+          "code": "450821000124107",
+          "system": "http://snomed.info/sct",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "450821000124107",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+
+        {
+          "code": "56578002",
+          "system": "http://snomed.info/sct",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "56578002",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+
+        {
+          "code": "56771006",
+          "system": "http://snomed.info/sct",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "56771006",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+
+        {
+          "code": "59978006",
+          "system": "http://snomed.info/sct",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "59978006",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+ 
+        {
+          "code": "65568007",
+          "system": "http://snomed.info/sct",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "65568007",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+
+        {
+          "code": "77176002",
+          "system": "http://snomed.info/sct",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "77176002",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+
+        {
+          "code": "82302008",
+          "system": "http://snomed.info/sct",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "82302008",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        }
+      ]
+    }
+  }
+}
\ No newline at end of file
diff --git a/test/fixtures/2.16.840.1.113883.3.600.2390-oid-vsdb.json b/test/fixtures/2.16.840.1.113883.3.600.2390-oid-vsdb.json
new file mode 100644
index 0000000..ab31c07
--- /dev/null
+++ b/test/fixtures/2.16.840.1.113883.3.600.2390-oid-vsdb.json
@@ -0,0 +1,140 @@
+{
+  "2.16.840.1.113883.3.600.2390": {
+    "20210304": {
+      "oid": "2.16.840.1.113883.3.600.2390",
+      "version": "20210304",
+      "codes": [
+        {
+          "code": "160603005",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "160604004",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "160605003",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "160606002",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "160619003",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "230059006",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "230060001",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "230062009",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "230063004",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "230064005",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "230065006",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "266920004",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "365981007",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "365982000",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "428041000124106",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "428061000124105",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "428071000124103",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "449868002",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "450811000124104",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "450821000124107",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "56578002",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "56771006",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "59978006",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "65568007",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "77176002",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        },
+        {
+          "code": "82302008",
+          "system": "urn:oid:2.16.840.1.113883.6.96",
+          "version": "http://snomed.info/sct/731000124108/version/20230901"
+        }
+      ]
+    }
+  }
+}
\ No newline at end of file
diff --git a/test/svs-test.js b/test/svs-test.js
index 6b303f8..b825569 100644
--- a/test/svs-test.js
+++ b/test/svs-test.js
@@ -7,9 +7,21 @@ const chai = require('chai');
 const should = chai.should();
 const temp = require('temp');
 const TOBACCO_VS_DB = fixVSDBFixture(require('./fixtures/2.16.840.1.113883.3.600.2390-vsdb.json'));
+const TOBACCO_OID_VS_DB = fixVSDBFixture(
+  require('./fixtures/2.16.840.1.113883.3.600.2390-oid-vsdb.json')
+);
+const TOBACCO_OID_URI_VS_DB = fixVSDBFixture(
+  require('./fixtures/2.16.840.1.113883.3.600.2390-oid-uri-vsdb.json')
+);
 const SYSTOLIC_VS_DB = fixVSDBFixture(
   require('./fixtures/2.16.840.1.113883.3.526.3.1032-vsdb.json')
 );
+const SYSTOLIC_OID_VS_DB = fixVSDBFixture(
+  require('./fixtures/2.16.840.1.113883.3.526.3.1032-oid-vsdb.json')
+);
+const SYSTOLIC_OID_URI_VS_DB = fixVSDBFixture(
+  require('./fixtures/2.16.840.1.113883.3.526.3.1032-oid-uri-vsdb.json')
+);
 
 describe('SVS', () => {
   let tmpCache;
@@ -124,6 +136,144 @@ describe('SVS', () => {
       );
     });
 
+    it('should merge value sets into the value set database, using default url options when empty options is included', async () => {
+      nock('https://vsac.nlm.nih.gov')
+        .get('/vsac/svs/RetrieveValueSet')
+        .basicAuth({ user: 'apikey', pass: 'testkey' })
+        .query({
+          id: '2.16.840.1.113883.3.526.3.1032'
+        })
+        .replyWithFile(200, path.join(__dirname, 'fixtures', '2.16.840.1.113883.3.526.3.1032.xml'))
+        .get('/vsac/svs/RetrieveValueSet')
+        .basicAuth({ user: 'apikey', pass: 'testkey' })
+        .query({
+          id: '2.16.840.1.113883.3.600.2390'
+        })
+        .replyWithFile(200, path.join(__dirname, 'fixtures', '2.16.840.1.113883.3.600.2390.xml'));
+
+      const vsDB = {};
+      await Promise.all([
+        svs.downloadValueSet(
+          'testkey',
+          '2.16.840.1.113883.3.526.3.1032',
+          undefined,
+          tmpCache,
+          vsDB,
+          true,
+          {}
+        ),
+        svs.downloadValueSet(
+          'testkey',
+          '2.16.840.1.113883.3.600.2390',
+          undefined,
+          tmpCache,
+          vsDB,
+          true,
+          {}
+        )
+      ]);
+      // Should add the results to the VS DB
+      Object.keys(vsDB).should.have.length(2);
+      vsDB['2.16.840.1.113883.3.526.3.1032'].should.eql(
+        SYSTOLIC_VS_DB['2.16.840.1.113883.3.526.3.1032']
+      );
+      vsDB['2.16.840.1.113883.3.600.2390'].should.eql(
+        TOBACCO_VS_DB['2.16.840.1.113883.3.600.2390']
+      );
+    });
+
+    it('should merge value sets into the value set database while maintaining original system', async () => {
+      nock('https://vsac.nlm.nih.gov')
+        .get('/vsac/svs/RetrieveValueSet')
+        .basicAuth({ user: 'apikey', pass: 'testkey' })
+        .query({
+          id: '2.16.840.1.113883.3.526.3.1032'
+        })
+        .replyWithFile(200, path.join(__dirname, 'fixtures', '2.16.840.1.113883.3.526.3.1032.xml'))
+        .get('/vsac/svs/RetrieveValueSet')
+        .basicAuth({ user: 'apikey', pass: 'testkey' })
+        .query({
+          id: '2.16.840.1.113883.3.600.2390'
+        })
+        .replyWithFile(200, path.join(__dirname, 'fixtures', '2.16.840.1.113883.3.600.2390.xml'));
+
+      const vsDB = {};
+      await Promise.all([
+        svs.downloadValueSet(
+          'testkey',
+          '2.16.840.1.113883.3.526.3.1032',
+          undefined,
+          tmpCache,
+          vsDB,
+          true,
+          { svsCodeSystemType: 'oid' }
+        ),
+        svs.downloadValueSet(
+          'testkey',
+          '2.16.840.1.113883.3.600.2390',
+          undefined,
+          tmpCache,
+          vsDB,
+          true,
+          { svsCodeSystemType: 'oid' }
+        )
+      ]);
+      // Should add the results to the VS DB
+      Object.keys(vsDB).should.have.length(2);
+      vsDB['2.16.840.1.113883.3.526.3.1032'].should.eql(
+        SYSTOLIC_OID_VS_DB['2.16.840.1.113883.3.526.3.1032']
+      );
+      vsDB['2.16.840.1.113883.3.600.2390'].should.eql(
+        TOBACCO_OID_VS_DB['2.16.840.1.113883.3.600.2390']
+      );
+    });
+
+    it('should merge value sets into the value set database while including both uri and oid versions of codes', async () => {
+      nock('https://vsac.nlm.nih.gov')
+        .get('/vsac/svs/RetrieveValueSet')
+        .basicAuth({ user: 'apikey', pass: 'testkey' })
+        .query({
+          id: '2.16.840.1.113883.3.526.3.1032'
+        })
+        .replyWithFile(200, path.join(__dirname, 'fixtures', '2.16.840.1.113883.3.526.3.1032.xml'))
+        .get('/vsac/svs/RetrieveValueSet')
+        .basicAuth({ user: 'apikey', pass: 'testkey' })
+        .query({
+          id: '2.16.840.1.113883.3.600.2390'
+        })
+        .replyWithFile(200, path.join(__dirname, 'fixtures', '2.16.840.1.113883.3.600.2390.xml'));
+
+      const vsDB = {};
+      await Promise.all([
+        svs.downloadValueSet(
+          'testkey',
+          '2.16.840.1.113883.3.526.3.1032',
+          undefined,
+          tmpCache,
+          vsDB,
+          true,
+          { svsCodeSystemType: 'both' }
+        ),
+        svs.downloadValueSet(
+          'testkey',
+          '2.16.840.1.113883.3.600.2390',
+          undefined,
+          tmpCache,
+          vsDB,
+          true,
+          { svsCodeSystemType: 'both' }
+        )
+      ]);
+      // Should add the results to the VS DB
+      Object.keys(vsDB).should.have.length(2);
+      vsDB['2.16.840.1.113883.3.526.3.1032'].should.eql(
+        SYSTOLIC_OID_URI_VS_DB['2.16.840.1.113883.3.526.3.1032']
+      );
+      vsDB['2.16.840.1.113883.3.600.2390'].should.eql(
+        TOBACCO_OID_URI_VS_DB['2.16.840.1.113883.3.600.2390']
+      );
+    });
+
     it('should error if value set is not found', async () => {
       nock('https://vsac.nlm.nih.gov')
         .get('/vsac/svs/RetrieveValueSet')