Total Hip and Total Knee Replacement Outpatient (THKR-OP)

THKR-OP Initial Patient Population

The THKR measure set is unique in that there are two distinct strata within the measure set, each identified by a specific group of CPT® Codes with Modifier, or lack thereof. The patients in each stratum are counted in the Initial Patient Population of multiple measures. The outpatient population is defined as a patient who is not hospitalized overnight but who visits a hospital, clinic, or associated facility for diagnosis or treatment. CPT® codes are utilized to bill outpatient cases when the patient undergoes a procedure. Any patient who has outpatient surgery that is billed using a CPT® code should be assigned to the outpatient bucket to determine patient volumes and cases for abstraction within the THKR performance measures.

The population of the THKR-OP measure set is identified using 4 data elements:

• CPT® Codes with Modifier
• Outpatient Encounter Date
• ICD-10-CM Principal or Other Diagnosis Code
• Birthdate

Patients seen in the outpatient setting are included in the THKR-OP measure set if they have:

CPT® Codes with Modifier is at least one on Appendix A, Table 14.01b, 14.02b, 14.03b, 14.04b, a Patient Age (Outpatient Encounter Date minus Birthdate) greater than or equal to 18 years, CPT® Codes with Modifier is none on Appendix A, Table 14.05b, 14.06b, 14.07b, and an ICD-10-CM Principal or other Diagnosis Code is none on Table 14.08, 14.09.

And are eligible to be sampled for:

1 – Stratum 1 – If patients have CPT® Codes with Modifier as defined in Appendix A, Table 14.01b, 14.03b are included in the THKR-OP stratum-1 and are eligible to be sampled.

2 – Stratum 2 – If patients have CPT® Codes with Modifier on as defined in Appendix A, Table 14.02b, 14.04b.are included in the THKR-OP stratum-2 and are eligible to be sampled.

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Initial Patient Population Algorithm

Total Hip And Total Knee Replacement Outpatient Initial Patient Population Algorithm Narrative

Variable Key: Patient Age on Outpatient Encounter Date, OP Initial Patient Population Reject Case Flag

1. Start THKR Outpatient Initial Patient Population logic sub-routine. Process all cases that have successfully reached the point in the Data Processing Flow which calls this Initial Patient Population Algorithm. Do not process cases that have been rejected before this point in the Data Processing Flow.

2. Check CPT® Codes with Modifier

1. If CPT® Codes with Modifier are All Missing or None on Table 14.01b, 14.02b, 14.03b, 14.04b, the patient is not in the THKR Outpatient Initial Patient Population. Patient is not eligible to be sampled for the THKR Outpatient measure set. Set OP Initial Patient Population Reject Case Flag to equal Yes. Return to Data Processing Flow section.
2. If CPT® Codes with Modifier has At least one on Table 14.01b, 14.02b, 14.03b, 14.04b, continue processing and proceed to calculate Patient Age on Outpatient Encounter Date.

3. Calculate Patient Age on Outpatient Encounter Date, in years, is equal to the Outpatient Encounter Date minus the Birthdate. Use the month and day portion of outpatient encounter date and birthdate to yield the most accurate age.

4. Check Patient Age on Outpatient Encounter Date:

1. If the Patient Age on Outpatient Encounter Date is less than 18 years, the patient is not in the THKR Outpatient Initial Patient Population. Patient is not eligible to be sampled for the THKR Outpatient measure set. Set OP Initial Patient Population Reject Case Flag to equal Yes. Return to Data Processing Flow section.
2. If the Patient Age on Outpatient Encounter Date is greater than or equal to 18 years, continue processing and proceed to check CPT® Codes with Modifier.

5. Check CPT® Codes with Modifier

1. If the CPT® Codes with Modifier has At least one on Table 14.05b, 14.06b, 14.07b, the patient is not in the THKR Outpatient Initial Patient Population. Patient is not eligible to be sampled for the THKR Outpatient measure set. Set OP Initial Patient Population Reject Case Flag to equal Yes. Return to Data Processing Flow section.
2. If the CPT® Codes with Modifier is None on Table 14.05b, 14.06b, 14.07b, continue processing and proceed to check ICD-10-CM Principal or Other Diagnosis Codes.

6. Check ICD-10-CM Principal or Other Diagnosis Codes

1. If the ICD-10-CM Principal or Other Diagnosis Codes has At least one on Table 14.08, 14.09, the patient is not in the THKR Outpatient Initial Patient Population. Patient is not eligible to be sampled for the THKR Outpatient measure set. Set OP Initial Patient Population Reject Case Flag to equal Yes. Return to Data Processing Flow section.
2. If the ICD-10-CM Principal or Other Diagnosis Codes are None on Table 14.08, 14.09, patient is in the THKR Outpatient Initial Patient Population. Set OP Initial Patient Population Reject Case Flag is equal to No. Continue processing and proceed to check CPT® Codes with Modifier.

7. Check CPT® Codes with Modifier

1. If the CPT® Codes with Modifier is On Table 14.02b, 14.04b, Patient is in the 2nd THKR Outpatient stratum. Patient is eligible to be sampled for the 2nd THKR Outpatient stratum. Return to Data Processing Flow section.
2. If the CPT® Codes with Modifier is On Table 14.01b, 14.03b, Patient is in the 1st THKR Outpatient stratum. Patient is eligible to be sampled for the 1st THKR Outpatient stratum. Return to Data Processing Flow section.

Sampling / Sample Size Requirements

Abstract a minimum of 10 outpatient hip cases and 10 outpatient knee cases per month (e.g. 20 cases for July, 20 cases for August, etc.).

• If a site has a monthly population of 10 or less outpatient hip cases, abstract all outpatient hip cases. Similarly, if 10 or less outpatient knee cases per month were performed, abstract all outpatient knee cases.
• If a site has a monthly population of greater than 10 outpatient hip cases, it is acceptable to abstract a sample of 10 hip cases. Similarly, if more than 10 outpatient knee cases per month were performed, it is acceptable to abstract a sample of 10 knee cases.

Sampling is a process of selecting a representative part of a population in order to estimate the organization’s performance, without collecting data for its entire population. Using a statistically valid sample, an organization can measure its performance in an effective and efficient manner. Sampling is a particularly useful technique for performance measures that require primary data collection from a source such as the medical record. Sampling should not be used unless the organization has a large number of cases in the Initial Patient Population because a fairly large number of sample cases are needed to achieve a representative sample of the population. For the purpose of sampling the project measures, the terms “sample” and “case” are defined as: “sample” is the fraction of the population that is selected for further study; “case” refers to a single record (or an episode of care [EOC]) within the population. Organizations are NOT required to sample their data. If sampling offers minimal benefit (i.e., a hospital has 13 cases for the month and must select a sample of 10 cases), the organization may choose to use all cases.

Sampling Approaches Simple random sampling - selecting a sample size (n) from a population of size (N) in such a way that every case has the same chance of being selected. Systematic random sampling - selecting every kth record from a population of size N in such a way that a sample size of n is obtained, where k ≤ N/n. The first sample record (i.e., the starting point) must be randomly selected before taking every kth record. This is a two-step process: a) randomly select the starting point by choosing a number between one and k using a table of random numbers or a computer-generated random number; and b) then select every kth record thereafter until the selection of the sample size is completed.

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