Turbidity Information and Courses from MediaLab, Inc.

Spinal fluid samples are either clear or turbid. Some sources use the following rating system for turbid CSF specimens: 0 = crystal clear fluid 1+ = faintly cloudy, smoky, or hazy 2+ = turbidity clearly visible but newsprint read easily through tube 3+ = newsprint not easily read through tube 4+ = newsprint cannot be seen through the tubeTurbidity may be caused by leukocytes, erythrocytes, fungi, bacteria, amoebae, contrast media, or aspiration of epidural fat during puncture.200 leukocytes/mm3 will cause slight turbidity (1+); increased numbers of WBCs will cause increased turbidity. At least 400 erythrocytes/mm3 are needed to produce 1+ turbidity.Occasionally CSF will have an oily appearance due to the presence of substances remaining in the CSF after radiologic (x-ray) procedures have been performed.

There are several acids which can be used to precipitate proteins - sulfosalicylic, trichloroacetic, nitric, and acetic acids. Sulfosalicylic acid (SSA) is the most frequently used acid test because it does not require the use of heat. Exton’s reagent is 5% sulfosalicylic acid in a solution of sodium sulfate. Exton (1925) found that adding sodium sulfate to the SSA causes a more uniform precipitate to be formed. To perform the SSA procedure mix equal parts of patient urine and the reagent. Rate the amount of turbidity according to the following scale:

Illustrated in this composite photograph is the gram stain of Enterococcus species (upper), illustrating gram positive cocci arranged in pairs and short chains.The viridans streptococci generally form gram positive cocci in long chains; the gram-positive cells of S. pneumoniae, on the other hand, may appear similar in gram stain.In the lower right is shown a 6.5% NaCl tube. The turbidity indicates growth, a unique characteristic for Enterococcus species.In the lower left frame is a picture of a bile esculin hydrolysis slant, showing a positive reaction (black pigment) characteristic of Enterococcus species. The streptococci are uniformly negative.Some strains of Leuconostoc species and Pediococcus species can grow in 6.5% NaCl and are bile-esculin positive; however, they should be ruled out because of the negative PYR reaction.

Particle-enhanced turbidimetric inhibition immunoassay (PETINIA) is a homogeneous competitive immunoassay.Antibody fragments and drug-latex particles will bind to form aggregates that increase the turbidity of the solution. Free drug from the sample competes for the antibody fragment, thereby decreasing the rate of particle aggregation. The rate of aggregation is inversely proportional to the concentration of drug in the sample.

The results are abnormal. The presence of glucose is not a normal finding. However, the two glucose methods correlate well with each other.The specific gravity does not correlate well with the glucose. A large amount of glucose should elevate the urine specific gravity. The specific gravity result should therefore be rechecked before reporting. The presence of 3+ bacteria, does not correlate well with scant white cells and lack of turbidity. The technologist should question whether the specimen was held at room temperature for a protracted period prior to examination.