Statistical Quality Control in Clinical Laboratories

The perceptions about quality, methods of its evaluation, and control have undergone a great evolution during the twentieth century. The need of the hour is the “total quality management” (TQM). In the middle of the twentieth century, the need for necessary degree of accuracy in Biomedical Laboratories worldwide was realized. Belk and Sunderman (Am J Clin Path 17:853, 1947) and Wootton and King (Lancet 1:470, 1953) were the pioneers in reporting discordant results of constituents of blood and biological fluids returned by various clinical laboratories participating in the “quality control study.” Statistical quality control (SQC) is the way used to describe the set of statistical procedures and tools used by “quality control professionals.” For “medical professionals,” the word “quality” refers to the degree of accuracy of a clinical investigation in a biomedical laboratory. Just talking about solving quality issues is not enough. We need specific tools and protocols for making right quality decisions. In industry the quality is important in three main areas of production process, namely, (1) quality of design, (2) quality of conformance to design, and (3) quality of performance. Statistical quality control can be divided into three categories for the convenience of understanding it. These categories are known as: 1. Descriptive Statistics: It includes statistics such as mean, standard deviation, the range, etc. 2. Statistical Process Control (SPC): It involves inspecting a random sample of the output (determination) and deciding whether the outcome falls within the predetermined range. It answers whether the process is functioning properly or not. 3. Acceptance Sampling: It pertains to randomly inspecting the samples of goods (in industry) and results of biological investigations (in medical field) and deciding whether to accept or reject goods or batch of reports of biological determinations. All three of these statistical quality control categories are helpful in measuring and evaluating the quality of products or services. The quality control tools not only measure the value of a quality characteristic but help us in training the quality control professionals too. These also help us to identify a change or variation in some quality characteristic of the product or process. The tools in each of these categories provide different types of information for use in analyzing quality.