George N. Bowers

Ionized Calcium in Body Fluids

This article will review the methods currently available to the clinician and research worker for measuring the concentration of ionized calcium in various body fluids including whole blood, serum, plasma, urine, cerebrospinal fluid, milk, and synovial fluid. The methods to be reviewed are based on procedures involving bioluminescence, colorimetry and ion-selective electrodes. Emphasis will be given to the precision and, wherever possible, accuracy of each technique. Possible sources of error and interfering agents will be identified. Attention will be given to the recommended conditions for measuring ionized calcium in each body fluid. An assessment will be made of the theoretical and practical importance of measuring ionized calcium rather than total calcium and of its value in clinical medicine.

Measurement of Alkaline Phosphatase Activity

This chapter will discuss some practical aspects of alkaline phosphatase assays. While the remarks are based predominantly on experience gained with human blood serum, many of the points raised are also applicable to the assay of alkaline phosphatases from other sources.

ACID PHOSPHATASE MEASUREMENT IN THE CLINICAL LABORATORY

Dr. Shaw has asked me to review for you the nonimmunologic enzyme activity assays for acid phosphatase (ACP) measurements made on human serum or plasma that have been or are currently being employed in clinical laboratories. In addition, he has asked that I also share with you the results of our recently published studies on the purity of the commercially available substrates 4nitrophenyl phosphate, thymolphthalein monophosphate, and 1-naphthyl phosphate. By my own rough estimates, I believe the number of ACP activity measurements for patient care purposes in the United States to be over 8 million tests per year.* The many thousands of discrete laboratory loci where these ACP assays are performed can be judged from the number and types of clinical lab facilities in the United States, as shown in TABLE 1. Although I can find no recent survey data on the types of methods used in these thousands of laboratories, it is my guess that the majority of them are using one of the traditional enzymatic activity assays to measure predominantly prostatic acid phosphatase (PAP] in serum or plasma. For the most part, these methods employ one of the relatively more specific substrates for PAP or add L-( + )-tartrate if one of the less specific substrates is used. Although our concern today is with PAP, we should not forget that other ACPs are useful in clinical medicine. During the last month we performed total ACP/PAP assays on 124 inpatients, and 43 (35%) were elevated. Only 3 (2%) samples had PAP elevated alone, 17 (14%) had both PAP and ACP elevated, but another 23 (19%) had only total ACP elevated! In our attempts to provide better PAP measurements for detection and management of prostatic cancer, the laboratory community should not ignore the other ACP isoenzymes. A review of the chronologic development of these ACP/PAP enzymatic methods may help us to understand why some of these methods are utilized today.

State-wide hospital clinical laboratory plan for measuring cholinesterase activity for individuals suspected of exposure to nerve agent chemical weapons.

Background. Hospital laboratories currently lack the capacity to provide emergency determination of cholinesterase activity. Methods. We have developed a hospital-based 3-tiered system to test plasma for butyrylcholinesterase (BChE) activity and whole blood for red cell acetylcholinesterase (AChE) activity using available technology and personnel. Interagency communications, toxidrome definition, and patient triage will be coordinated by the Connecticut Department of Public Health and the Poison Control Center. Data. Initial BChE data documents good precision between institutions (coefficient of variation < 8%). Summary. Laboratory testing of plasma or blood for cholinesterase activity is important in the management of nerve agent exposure and in ruling out disease in those with non-specific symptoms in the setting of a terrorist attack or accidental exposure. Rapid availability of strong hospital-based analytic support in a smoothly functioning network of clinical, public health, and laboratory services will facilitate overall regional response to chemical terrorism or large scale HazMat events.

Introduction, General Aims, and Scope

This book brings together some of the vast amount of information that has accumulated in 70 years about the group of hydrolytic enzymes generally referred to as “alkaline phosphatase” [international classification: orthophosphoric monoester phosphohydrolase (alkaline optimum), 3.1.3.1].1 It is intended to serve as a reference text for physicians, clinical chemists, biochemists, veterinarians, biologists, and physiologists, as well as for workers in related areas.

The Clinical Application of Ionized Calcium

Some of the important milestones in the development of our ability to rapidly measure ionized calcium (Ca2+) in the whole blood, plasma, and serum to patients are listed in Table 1. The text also gives key references that can provide greater in-depth coverage for those wishing more detailed information.

Industrial and Other Uses

The phosphatase activity of the milk is usually higher than that of the plasma of the cow.1