About the COS-C Exam

Certificate for OASIS Specialist-Clinical (COS-C) Exam

The Certificate for OASIS Specialist-Clinical (COS-C) exam is the premier, nationally standardized, psychometrically validated test that evaluates an individual's knowledge of CMS' OASIS guidelines. The COS-C exam is a voluntary certificate examination available to home healthcare providers, who are interested in demonstrating and establishing their expertise and commitment to OASIS data accuracy. 

Areas covered by the COS-C exam include:

  • OASIS regulations
  • Data collection time points
  • Patient populations
  • Data collection conventions
  • OASIS data set item-by-item guidance

The COS-C exam was developed and administered by the OASIS Certificate & Competency Board (OCCB). Exam administrators go to great lengths to ensure that the exam is an accurate reflection of the most current CMS guidance, and that it is administered in a way to protect the integrity of the resulting COS-C designation. Since its inception more than 30,000 candidates have participated in the exam process.

How to Take the COS-C Exam

There are two ways to take the COS-C Exam, and the format and content are the same for both options. Register for the option that best suits your needs. To check the current listing of those who have successfully passed the COS-C Exam, Check COS-C Status.

  1. Paper & Pencil Test at Workshop Location
  2. Computer-Based Test at a Testing Center


COS-C Exam Details

  • Participation: The exam is open to all participants. There are no requirements other than a desire to demonstrate your knowledge of CMS data collection guidance and commitment to OASIS data accuracy. Suggested professions: Home Health Nurses, Therapists or other home healthcare professionals responsible for conducting comprehensive assessments, scoring OASIS items, auditing clinical records, educating or orienting staff
  • Exam Length: 2.5 hour exam duration, 100 multiple-choice questions. Exam results are reported as Pass or Fail. At Exam check-in, candidates must present 2 forms of Identification, one of which must be valid government-issued ID.
  • Exam Content: The scope of the COS-C exam includes CMS rules and instructions related to the OASIS time points, regulations, patient populations & OASIS item specific scoring. The exam is open-book; candidates are allowed to bring ANY paper-based OASIS reference materials into the examination, including, but not limited to, CMS Core OASIS Documents, OASIS Guidance Manual, CMS OASIS Q&A’s, the Blueprint for OASIS Accuracy handout and an Instant OASIS Answers book.

How to Prepare for the Exam

  • For details on how to prepare for the exam and sample test questions go to, Exam Preparation 
  • For exam instructions and protocols for each testing option refer to, Candidate Handbook

The Psychometric Process

The COS-C exam is reviewed and regularly updated, including regular item analysis to determine that all test items are performing as originally intended. Exam items are developed by the COS-C Exam Review Committee, a group of OASIS content experts of varied home health backgrounds and disciplines, who create these items to reflect the OASIS knowledge and skills identified as necessary for competent OASIS data collection. The test undergoes a holistic review by a psychometrician and the Committee examining the test for accuracy, significance, fairness, and conformity to test specifications.

A rigorous item analysis adhering to psychometric industry standards detects any questionable item performance. When item ambiguities are detected, the necessary adjustments are made before a passing score is determined. 

This extensive psychometric process is necessary not only to verify each item as reliable and an appropriate representation of CMS' rules but also to determine that all questions are written in an accurate and fair manner. How a question is asked is as important as what the question is asking. Knowing that the COS-C exam meticulously covers CMS' OASIS guidance is not enough. Only when we statistically verify that each item is psychometrically and technically sound and ensure the test is administered in a conducive and protected environment, does the exam attain credibility; credibility that bestows value upon the resulting COS-C designation.

Learn more by reading Insights from the COS-C Exam Psychometrician on our blog.