Author: Mary Hurley, CPC
Professional Coder – Pinnacle Integrated Coding Solutions

(303) 801-0111

If you have questions regarding the difference between a screening and a diagnostic test and when to bill for them separately-You are not alone!


Let’s start by going over the ICD-10’s Official Reporting Guidelines.  These state that screening tests are performed to test for disease or disease precursors in seemingly well individuals.  These tests are performed for early detection of disease to provide timely intervention and management so treatment can be provided for those who test positive for the disease.  One point to remember is that screenings may not always be beneficial, as results may show false positives, false negatives and result in misdiagnoses.


Next let’s look at how to code for screening tests.  Per ICD-10’s Official Reporting Guidelines, a screening code may be the first listed code if the reason for the visit is specifically for the screening exam.  It may be used as an additional code if the screening is done during an office visit for other health problems.  A screening code is not necessary if the screening is inherent to a routine examination, such as a pap smear done during a routine pelvic examination.  Should a condition be discovered during the screening, then the code for the condition may be assigned as an additional diagnosis.


The Z code indicates that a screening exam is planned.  A procedure code is required to confirm that the screening was performed.  The screening Z codes / categories are listed below:


Z11       Encounter for screening for infectious and parasitic diseases

Z12       Encounter for screening for malignant neoplasms

Z13       Encounter for screening for other diseases and disorders. Except: Z13.9, Encounter for screening, unspecified

Z36       Encounter for antenatal screening for mother


There are different categories for screening tests which are defined by the population on which the tests are performed, not the results or findings of the test.


  • Universal screening all individuals in a certain category (i.e. Colonoscopy patient age 50 or older)
  • Case finding–screening smaller groups based on the presence of risk factors (i.e. Family history)
  • High risk or selective–screening high risk populations (i.e. screening coal miners for black lung)


Now on to diagnostic tests. Per ICD-10’s Official Reporting Guidelines, the testing of a person to rule out or confirm a suspected diagnosis because the patient has some sign or symptom is a diagnostic examination, not a screening.  In these cases, the sign or symptom is used to explain the reason for the test.


Diagnostic tests are also performed to identify areas of weakness and strength to determine a condition, disease or illness to provide the appropriate treatment in patients that are symptomatic or asymptomatic with a positive screening.  Diagnostic testing is beneficial as the results provide a definite diagnosis.  Diagnostic tests such as x-rays, biopsies, CT scans or MRI are used to gather clinical information for making a clinical decision / diagnosis.


Now comes the fun part!


When coding for diagnostic tests you should code the confirmed diagnosis whenever possible.  The confirmed diagnosis should be based on the results of the diagnostic test.  If there is no confirmed diagnosis or the results are normal, you should code the signs and symptoms which would probably be the reason for the test.  You should never list any incidental findings as a primary diagnosis.  Any unrelated and / or coexisting conditions should be listed as secondary diagnoses.


Case Example#1:

A 50+ year old woman comes in for her annual mammogram.  Since this is a routine screening with no reported symptoms, assign ICD-10 code Z12.31.


The CPT code for this is 77067, screening mammography, bilateral (2-view study of each breast), including computer-aided detection (CAD) when performed.


If the patient had presented with signs/symptoms this would be a diagnostic mammogram. You would use the CPT code 77065 for mammography, including computer-aided detection (CAD) when performed, unilateral or 77066 for bilateral. For the diagnosis you would use the result of the study or if normal, then code the reason for the encounter (sign or symptom).


Another example is a colonoscopy which can be performed as a screening for adults 50 years or older. A colonoscopy examines the entire colon, from the rectum to the cecum and may include the examination of the terminal ileum or small intestine proximal to an anastomosis, in which case you would use CPT code 45378. CPT code 45378 can be used for screening and diagnostic colonoscopies, but if the entire colon is not examined due to unforeseen circumstances and the provider is not able to advance the colonoscope to the cecum or colon-small intestine anastomosis you should report 45378 with modifier 53.


Case Example#2:

50+ year old gentleman who is being seen for a screening colonoscopy. Since it is just a screening, no signs or symptoms have been reported. If the results are normal, you would use a Z12 diagnosis code.  If there are signs, symptoms or the results of the screening colonoscopy are abnormal then it would be appropriate to perform a diagnostic colonoscopy.  You should also note that the CPT Guidelines under Endoscopy would be followed when coding any of these colonoscopies.


The last example pertains to screening coal miners for Black Lung Disease, also known as Coal Worker’s Pneumoconiosis.  This is a lung disease due to exposure to coal dust that afflicts coal miners, making this population most at risk for Black Lung.  The Federal Black Lung Program (which falls under the Department of Labor Black Lung Benefits Act of 1973) provides screenings for Coal Miners to detect early signs of Black Lung and/or other pulmonary diseases which occur when working in coal mines. You would use procedure code 71250 (CT, Thorax; without contrast material) for reimbursement.  Again, timely detection allows early treatment which has lowered the mortality rate of coal miners.  If the screening test is normal, then Z12.2 should be used for the diagnosis but if an abnormality is detected then more diagnostic testing would be performed, i.e., chest X-rays, MRI, PET scans, etc.


To sum it all up, screenings are performed to detect diseases early for timely treatment and to prevent disease manifestations in an asymptomatic patient.  Diagnostic testing is performed when there is a sign or symptom of a disease, which will prove beneficial to the course of treatment, depending on the severity or manifestation.  Understanding these screening differences makes you a more skillful coder and allows you to be prudent to take full advantage of screenings if or when they are available.