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# Lab quality

Definition | Term |
---|---|

Statistically determined range of values within which a test result must fall to be considered acceptable; it is a means of QC or QA | Acceptable Control Range |

Correctness of a result, freedom from error, or how close the answer is to the ‘true’ value | Accuracy |

Process whereby analytical analyses are carried out; includes generating work lists, doing the analyses, entering the results, QC measures, and result verification. | Analytic Functions |

Solutions made with dry chemicals that do not contain any water molecules. | Anhydrous Solutions |

The inverse logarithm of a number | Antilog |

Means by which a laboratory apparatus is checked to determine the exact units it will measure or deliver by relating them to a known concentration of an analyte | Calibration |

Used to compare the standard deviations of a group of samples; in percent, this is equal to the standard deviation divided by the mean; A measure of precision Formula = SD/Mean x 100 | Coefficient of Variation – CV |

A value used to express or estimate statistical parameter; an example is when the reference range is set using values 2 SD’s on either side of the mean, with 95% of the values falling above or below the mean. A 95% confidence interval. | Confidence limits (confidence interval) |

Material or solution with a known concentration of the analytes being measured; used for QC when the test result for the control specimen must be within certain limits for the unknown values (patients) to be considered reportable | Control Specimen |

The liquid that a sample is placed into in order to make a dilution. | Diluent |

Reciprocal of the dilution made; multiply the result by the reciprocal (denominator) of the dilution to correct for the dilution used. | Dilution Factor |

The scattering of the values of a frequency distribution from an average (mean) | Dispersion |

Those subjects who have a negative test yet DO have the disease | False Negatives |

Those subjects who have a positive test but do NOT have the disease | False Positives |

Particular symmetric statistical distribution, also known as a ‘normal’ distribution; statistically a toll used to set references ranges | Gaussian curve or Distribution |

The inverse of the exponential function y=a^. Consist of 2 parts: the Characteristic, which is the whole number; and the Mantissa, which is the decimal part. | Logarithm |

Statistically calculated mathematical average value for a valid series of numbers, as for a series of test results. The series of values is totaled and divided by the number in the series. | Mean |

The middle value of a body of data; the point that falls halfway between the highest and lowest in position. | Median |

The value that occurs most commonly in a mass of data | Mode |

The number of moles of solute per kilogram of solvent. Based off weight, not volume. | Molality |

Gram-molecular mass or weight of a compound per liter of solution. A 1 molar solution contains 1 mol of solute in 1L of solution | Molarity |

Number of equivalent weights per liter of solution. A 1 normality solution contains 1 equivalent weight in 1L solution. | Normality |

Includes functions that occur after the analyses itself, such as generating chart reports, printing result reports as needed, archiving results and billing. | Post-Analytical Function |

Functions in testing protocol that occur before the actual analyses – test ordering, specimen collection, and so forth. | Pre-Analytical Function |

Measure of the closeness of the results obtained when analysis on the same sample is repeated, agreement between replicate measurements. | Precision, Reproducibility |

Program under which samples are sent to a group of laboratories for analysis; results are compared with those of other laboratories participating in the program. Included as a component of QA programs. | Proficiency Testing or Survey |

Comprehensive set of policies, procedures, and practices necessary to make sure that a laboratories results are reliable. QA includes record keeping, calibration and maintenance of equipment, QC, proficiency testing, and training. | Quality Assurance QA |

Indicators that monitor the performance of a laboratory and are evaluated as part of continuous quality improvement | Quality Assurance Indicators |

Plan to carry out policies and practices necessary to comply with QA standards set by accreditation agencies to make certain that a laboratory’s results are reliable and that these results are used in the best interest of the patient. | Quality assurance program |

Set of laboratory procedures designed to ensure that a test method is working properly and that the results meet the diagnostic needs of the physician. QC includes testing control samples, charting the results, and analyzing them statistically. | Quality Control QC |

Visual documentation of information derived from using control specimens; values for control specimen assays used for a particular substance are plotted on the chart on a regular basis and are statistically analyzed for trends of change. | Quality Control Chart |

Plan to carry out procedures established to make certain that laboratory assay methods are working properly and that assay results meet the diagnostic needs of the physician; makes use of control specimens and standard solutions. | Quality Control Program |

Amount of something in proportion to an amount of something else; always describes a relative amount. | Ratio |

Any substance employed to produce a chemical reaction. | Reagent |

Range of values that includes 95% of the test results of a healthy reference population. | Reference Range/Normal Range/Reference values |

Ability of a laboratory assay to produce consistent results when testing is repeated successively. | Reliability |

The proportion of cases of having a specific disease or condition that give a positive test result. Only patients with the disease have the disease. | Sensitivity |

Progressive dilutions of a substance in a series of tubes in predetermined ratio to give concentrations of a specific amount | Serial Dilutions |

A term that describes when QC results are all distributed on one side of the mean or the other for 5-7 consecutive days. | Shift |

Statistical measurement of the degree of variation from the mean of a series of measurements; measure of precision or reproducibility. The square root of the variance. | Standard deviation |

A term that describes when quality control results either increase or decrease consistently over a period of time of 5-7 days. | Trend |

Those subjects who have a negative test and who do not have the disease. | True Negatives |

Those subjects who have a positive test and who have the disease. | True Positives |

An indication of the precision of a set of numbers. | Variance |

A set of QC rules that help the laboratory personnel decide when a QC value is ‘in control’ or ‘out of control’. | Westgard Multirules |

A warning rule where one of the 2 QC values fall outside of the plus 2 or minus 2 SD value. It is indicative of a random error. | 1-2s |

A rule that results in rejection of the QC results if one or more of the 2 QC values fall outside of the plus or minus 3SD. It is indicative of random error. | 1-3s |

Violated in 2 ways. The first is if 2 different QC levels analyzed in the same run and are outside the 2SD in the same direction. The second is if there are two 1-2s rule violations in a row for one level of control. Indicative of systematic error. | 2-2s |

A rule that is broken when the difference or range between 2 control values within a run is greater that 4SD. It is indicative of random error. | R-4s |

Violated in two ways. The first is when 4 values in a row of the same level of control all fall on the same side of the mean. The other way is when 2 levels of control are used in a run and each has had 2 values in a row fall on the same side of the mean. | 4-1s |

Violated in 2 ways. The first is when 10 consecutive values run for one level of control all fall on the same side of the mean. The other way is when the results are all on the same side of the mean for both QC levels for 5 days. | 10x |

These two rules are indicative of systematic error | 2-2s and 10x |

These 3 rules are indicative of random error | R-4s, 1-3s,1-2s |