Use of medians and "average of normals" of patients' data for assessment of long-term analytical stability

Using results from patients, we studied several methods for long-term (years) monitoring of the analytical stability of various chemistry tests. For each test, we obtained on a bimonthly basis histograms of > or = 200 to approximately 2000 data points and determined the median, mean, and mean of those data points in the reference range ("average of normal" or AON). Examining approximately 4 years' data, we found that the medians and AON are extremely stable for most tests, and that all observed shifts in the medians or in the AON could be explained by expected or unexpected changes in the laboratory. The means and peak values of the Erlang (gamma) distribution were less useful, owing to shifts caused by extreme outliers, especially for enzymes in serum. We assumed that the underlying patient population and testing patterns were stable. We recommend the use of medians or the AON of patients' data under defined conditions for monitoring the long-term analytical stability of certain tests involving serum or whole blood.

Use of medians and "average of normals" of patients' data for assessment of long-term analytical stability

Using results from patients, we studied several methods for long-term (years) monitoring of the analytical stability of various chemistry tests. For each test, we obtained on a bimonthly basis histograms of > or = 200 to approximately 2000 data points and determined the median, mean, and mean of those data points in the reference range ("average of normal" or AON). Examining approximately 4 years' data, we found that the medians and AON are extremely stable for most tests, and that all observed shifts in the medians or in the AON could be explained by expected or unexpected changes in the laboratory. The means and peak values of the Erlang (gamma) distribution were less useful, owing to shifts caused by extreme outliers, especially for enzymes in serum. We assumed that the underlying patient population and testing patterns were stable. We recommend the use of medians or the AON of patients' data under defined conditions for monitoring the long-term analytical stability of certain tests involving serum or whole blood.

Estimation of Reference Ranges: How Many Subjects are Needed?

We measured Na, K, Cl, glucose, hemoglobin, erythrocytes, and hematocrit in the serum or blood from approximately 800 male and 200 female second-year medical students in an effort to define the size of an acceptable reference population. Using the data from the men and Monte Carlo simulations of 10-400 samples, each carried out 5000 times, we found that for most of the above tests, approximately 200 people are required for stable lower (2.5%) and upper (97.5%) reference limits to be obtained. This agrees with the 198 subjects required by strictly statistical criteria to define the same limits with a 99% confidence level.

Estimation of reference ranges: how many subjects are needed?

We measured Na, K, Cl, glucose, hemoglobin, erythrocytes, and hematocrit in the serum or blood from approximately 800 male and 200 female second-year medical students in an effort to define the size of an acceptable reference population. Using the data from the men and Monte Carlo simulations of 10-400 samples, each carried out 5000 times, we found that for most of the above tests, approximately 200 people are required for stable lower (2.5%) and upper (97.5%) reference limits to be obtained. This agrees with the 198 subjects required by strictly statistical criteria to define the same limits with a 99% confidence level.

Herniated cervical disk presenting as ischemic chest pain

Myocardial ischemia must be the first concern of every emergency physician in evaluating chest pain in the adult patient. Any suspicion of myocardial ischemia must be promptly evaluated and admitted. The American College of Emergency Physicians has recently published a standards document on the care of chest pain in the adult patient. The emergency physician must be familiar with this document. Once myocardial ischemia and other life-threatening causes are ruled out, one can consider that cervical disk disease may be the cause of chest pain. The authors present two cases of patients who presented to the Emergency Department with signs and symptoms consistent with cardiac ischemia. Both patients were found to have herniated cervical disks. Subsequent surgical repair completely relieved their symptoms. Evaluation of the literature reveals that this entity was well described from 1950 to the 1960s. Most recent discussions do not mention disk herniation as even an infrequent cause of chest pain. If there is no life-threatening disease present, one should consider cervical disk disease.

Herniated cervical disk presenting as ischemic chest pain

Myocardial ischemia must be the first concern of every emergency physician in evaluating chest pain in the adult patient. Any suspicion of myocardial ischemia must be promptly evaluated and admitted. The American College of Emergency Physicians has recently published a standards document on the care of chest pain in the adult patient. The emergency physician must be familiar with this document. Once myocardial ischemia and other life-threatening causes are ruled out, one can consider that cervical disk disease may be the cause of chest pain. We present two cases of patients who presented to the emergency department with signs and symptoms consistent with cardiac ischemia. Both patients were found to have herniated cervical disks. Subsequent surgical repair completely relieved their symptoms. Evaluation of the literature shows that this entity was well described from 1950 to the 1960s. Most recent discussions do not mention disk herniation as even an infrequent cause of chest pain. If there is no life-threatening disease present, one should consider cervical disk disease.

Promotion of human T lymphocyte proliferation by IL-4

The capacity of human rIL-4 to support the proliferation of mitogen-stimulated T cells directly as well as by increasing IL-2 production or enhancing IL-2 responsiveness was investigated. IL-4 augmented proliferation of T cells stimulated with PHA, Con A, immobilized mAb to the CD3 molecular complex (OKT3), or PMA. IL-4 increased the number of mitogen-stimulated cells entering the cell cycle as well as enhancing ongoing proliferation of mitogen-activated lymphoblasts. Facilitation of initial activation by IL-4 was not inhibited by mAb to the p55 component of the IL-2R, anti-Tac, and, therefore, was not dependent on endogenous IL-2 activity. However, IL-4-mediated enhancement of ongoing T cell proliferation stimulated by PHA or OKT3 was partially but not completely blocked by anti-Tac. Analysis of the supernatants from PHA-stimulated T cell cultures indicated that IL-4 increased the production of IL-2 by mitogen-activated cells. Moreover, IL-4 increased the amount of IL-2 mRNA that accumulated in mitogen-stimulated T cells. In addition, IL-4 markedly augmented IL-2R expression by PHA-stimulated T cells. Although IL-4 promoted ongoing DNA synthesis of mitogen-stimulated T cells in an IL-2-dependent manner, it was also able to sustain their proliferation directly. Thus, IL-4 supported proliferation of PMA-activated T cells in a manner that was not inhibited by anti-Tac. Furthermore, IL-4 could augment proliferation and IL-2R expression of T cells stimulated with PHA in the presence of cyclosporin A, which blocks endogenous cytokine production or anti-Tac. Finally, IL-4 was noted to enhance proliferation of both CD4+ and CD8+ T cell subsets. The results indicate that IL-4 enhances proliferation of mitogen-activated human T cells by a number of mechanisms, including the direct promotion of cell cycle entry and subsequent DNA synthesis, enhanced production of IL-2, and increased responsiveness to IL-2 in part by up-regulation of IL-2R expression.

Promotion of human T lymphocyte proliferation by IL-4

The capacity of human rIL-4 to support the proliferation of mitogen-stimulated T cells directly as well as by increasing IL-2 production or enhancing IL-2 responsiveness was investigated. IL-4 augmented proliferation of T cells stimulated with PHA, Con A, immobilized mAb to the CD3 molecular complex (OKT3), or PMA. IL-4 increased the number of mitogen-stimulated cells entering the cell cycle as well as enhancing ongoing proliferation of mitogen-activated lymphoblasts. Facilitation of initial activation by IL-4 was not inhibited by mAb to the p55 component of the IL-2R, anti-Tac, and, therefore, was not dependent on endogenous IL-2 activity. However, IL-4-mediated enhancement of ongoing T cell proliferation stimulated by PHA or OKT3 was partially but not completely blocked by anti-Tac. Analysis of the supernatants from PHA-stimulated T cell cultures indicated that IL-4 increased the production of IL-2 by mitogen-activated cells. Moreover, IL-4 increased the amount of IL-2 mRNA that accumulated in mitogen-stimulated T cells. In addition, IL-4 markedly augmented IL-2R expression by PHA-stimulated T cells. Although IL-4 promoted ongoing DNA synthesis of mitogen-stimulated T cells in an IL-2-dependent manner, it was also able to sustain their proliferation directly. Thus, IL-4 supported proliferation of PMA-activated T cells in a manner that was not inhibited by anti-Tac. Furthermore, IL-4 could augment proliferation and IL-2R expression of T cells stimulated with PHA in the presence of cyclosporin A, which blocks endogenous cytokine production or anti-Tac. Finally, IL-4 was noted to enhance proliferation of both CD4+ and CD8+ T cell subsets. The results indicate that IL-4 enhances proliferation of mitogen-activated human T cells by a number of mechanisms, including the direct promotion of cell cycle entry and subsequent DNA synthesis, enhanced production of IL-2, and increased responsiveness to IL-2 in part by up-regulation of IL-2R expression.