General Grading Procedures
Grading procedures must conform to the February 28, 1992 Final Rule which implements the Clinical Laboratory Improvement Amendments ’88. This rule retains two practices previously mandated regulations from Centers for Medicaid and Medicare Services (CMS):
- 1. The principle of peer grading (participant consensus) determines target values (satisfactory performance), especially for quantitative results.
2. The principle of medical (fixed) performance standards primarily determines grading limits, but not to the total exclusion of the principle of methodological (statistical) performance standards. The major aspects of grading procedures are detailed to follow.
The grading of all results depends on the existence of a consensus of acceptable results. For most analytes or procedures, CMS defines consensus as acceptable performance among 80% or more of results from all participants or referees. Per CMS guidelines, if 80% consensus is achieved among all laboratories or referee laboratories, then the analyte must be graded. Exceptions to this rule exist for all CMS-scored procedures in Immunohematology, in which consensus is defined as agreement among 95% or more of results from all participants or referees.
Special Grading Formulas in Microbiology
When consensus grading is applied to microbiology modules in which more than one response may be reported for a given procedure in the same specimen, special formulas for generating percent scores for each specimen are mandated by the February 28 Rule of 1992. These formulas thus govern the grading of organism identifications and/or antimicrobial susceptibilities in Bacteriology, GC Culture, Parasitology, Throat, Throat/Urine and Urine Culture programs. For scoring organism identifications in a given specimen, the following ratio of responses is multiplied by 100:
- 1. The numerator is the sum of all gradable correct participant responses. Only one participant response per organism is counted, and, in cases in which more than one response is given per organism, only the most definitive answer is used. For example, a species name takes precedence over a genus name which, in turn, takes precedence over an antigen screen result which, in turn, takes precedence over a Gram stain result.
2. The denominator is the sum of all incorrect responses for the presence of organisms plus the total number of gradable correct responses for the specimen.
Since AAB determines which organism(s) to place in each specimen, AAB determines the total number of gradable correct responses for the presence of organisms.
For scoring antimicrobial susceptibilities in a given specimen, the following ratio of responses is multiplied by 100:
- 1. The numerator is the sum of all gradable correct responses.
2. The denominator is the sum of all gradable correct responses.
Since each participant determines which antimicrobials to report on their patient specimens, each participant determines the total number of antimicrobial susceptibilities to report on PT specimens. The only reporting requirement is that the susceptibilities reported on a proficiency test specimen reflect the same list of drugs which would be tested by the laboratory on patient material in the same clinical context as that of the proficiency specimen.
Peer Groups for Quantitative Results
To provide optimal peer grading, quantitative results are grouped initially by coupling reagent and instrument. After outlier removal, if the group shows poor precision, a second grouping by reagent alone is applied. If a third group is required, method principle or calibration type is employed. If no information is provided concerning reagent and instrument, or if the group is not statistically viable, results are graded by total population. This style of grading is used for Alcohol, Basic/Comprehensive Chemistry, Coagulation, Direct Bilirubin, Fertility Endocrinology, Fructosamine, Glycohemoglobin, Isoenzymes, Lipids, Special Chemistry, Therapeutic Drug Monitoring and Urine Microalbumin. Other quantitative modules are grouped initially by instrument or method, second by method principle and finally by total population. This scheme applies to Activated Clotting Time, Blood Gases, Centrifugal Hematology (QBC), C Reactive Protein, Hematology, Immunoproteins, Urinalysis, Whole Blood Glucose, Whole Blood Prothrombin Time, Andrology and Embryology programs.
Reference Method Values
Reference method values for Cholesterol (HDL, LDL and Total) and Triglycerides are published in our Participant Statistics for informational purposes only. They are not used in grading in any fashion. We gratefully acknowledge Atherotech, Inc. for providing these values.
“Would Refer” is a special response available for some interpretive programs such as Microbiology, Clinical Microscopy or Hematology with Manual Differential. It represents the situation where you would refer a non-routine result on to another entity such as a reference laboratory or pathologist for further interpretation or for a final result. You may only enter this response if this is your laboratory’s standard procedure for handling patient samples with similar results. You may not enter “Would Refer” for all 5 specimens in these programs unless you are not performing any patient testing of the same type at the time of the proficiency testing event. If you do report “Would Refer” for all 5 specimens, you will be graded as having discontinued testing for the current testing event only.
For more information or to view the Table of Grading Limits, download our Program Guide.