Nitrogen Information and Courses from MediaLab, Inc.

False negative results may occur in urine specimens that did not remain in the bladder a sufficient length of time for the bacteria to reduce a measurable quantity of nitrate to nitrite. Other reasons for false negative results include high specific gravity, ascorbic acid levels above 25mg/dL or low pH (<6). Less frequently, the cause may be due to a lack of sufficient nitrate in the diet (green vegetables) or further reduction of nitrite to nitrogen when large numbers of bacteria are present. In patients receiving antibiotics, the metabolism of the bacteria may be inhibited which would also produce a false negative reaction.

Although not performed that often, the following tests are useful in separating E. corrodens from other closely related members of the HACEK group:KIA showing an alk/alk reaction; Glucose fermentation (-); Reduction of nitrates to nitrites (+); Production of indole (-); Ornithine decarboxylase (+) The positive nitrate reduction reaction eliminates Cardiobacterium hominis, Kingella kingae and other Kingella species.The positive ornithine decarboxylase reaction eliminates Kingella denitrificans (which also denitrifies nitrate to nitrogen gas, a reaction negative for E. corrodens).Eikenella corrodens is asaccharolytic, whereas most other closely related species produce acid from one or more carbohydrates.

Here are the criteria for the preparation of tables, as specified by the Journal of Clinical Laboratory Science: Write table titles at the top of the table. Number tables sequentially with Roman numerals. Include the following information in a title, whenever possible: who, what, where, why and when. Put the independent variable in the left column, and the dependent variable in the right, if you are listing data with independent and dependent variables. Label each column with the appropriate units. Adequately space tables that appear on the same page. Example:Table I Patient specimens analyzed for blood urea nitrogen on the Dimension RxL and the Vitros 250 at City Hospital Sample # RxL (mg/dL urea) Vitros 250 (mg/dl) urea 1 8.8 8.8 2 11.2 10.0 3 12.4 13.6 4 16.2 13.2 5 20.0 21.2 6 25.0 20.0 7 28.8 26.2 In this case, the Dimension RxL is the "reference method" and is considered the independent variable, while the Vitros 250 is the "test method" and is considered the dependent variable.

The first step in calculating the standard deviation is to calculate the mean, x. In this case, x = 10.Now, subtract that mean from each of the data values, and then square those results:Table VII Urea Nitrogen Concentration in 5 Employees (mg/dL) Concentration (mg/dL) x- (x-)2 9 -1 1 7 -3 9 11 1 1 13 3 9 10 0 0 Total 20 Use this total to calculate the standard deviation:The standard deviation is about 2.23.

As stated before, many of the measurements you make will be approximately normally distributed. If you plot your data, and they fall roughly in the bell curve shape, then you can make the assumption that your underlying population distribution is normal.Using this assumption, you can make several inferences about your population based on the sample data. First, approximate the population mean ì with the sample mean, , and the population standard deviation s with the sample standard deviation, s. Then you can say that 68% of all data from the population will be within 1s of , 95% within 2s, and 99% within 3s. An example will illustrate.Suppose you have urea nitrogen data with a sample mean of 15 mg/dL, and a sample standard deviation of 5 mg/dL. Then the following is true: approximately 68% of healthy people will have urea nitrogen in the range ± 1s = 15 ± 5 mg/dL = 10-20 mg/dL. approximately 95% of healthy people will have urea nitrogen in the range ± 2s = 15 ± 10 mg/dL = 5-25 mg/dL. approximately 99% of healthy people will have urea nitrogen in the range ± 3s = 15 ± 15 mg/dL = 0-30 mg/dL. These data can be used to set standards for healthy urea nitrogen levels. Most labs set the 95% window as reference ranges for all tests performed

Consists of an electrolyte panel, plus: Blood urea nitrogen (BUN), which a measure of renal function. Creatinine (Creat), which also measures renal function Glucose, the most important blood sugar, and Calcium. Run on serum or plasma