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Inoculating from a broth culture is not recommended because the inoculum would be too heavy. If the organism has the ability to use citrate, the medium usually changes its color from green to blue, though growth on the medium even without colour change is considered a positive result. [1] An observation of no growth is a negative result.
The color change to blue is useful because growth on Simmons' citrate agar is often limited and would be hard to observe if it were not for the color change. Sometimes, it is possible to detect growth on the Simmons' citrate agar without the accompanying color change to blue. This should be scored as a negative for the citrate use test. [12]
Blood is drawn into a test tube containing liquid sodium citrate, which acts as an anticoagulant by binding the calcium in a sample. The blood is mixed, then centrifuged to separate blood cells from plasma (as prothrombin time is most commonly measured using blood plasma). In newborns, a capillary whole blood specimen is used. [2]
Sodium citrate is used to prevent donated blood from clotting in storage, and can also be used as an additive for apheresis to prevent clots forming in the tubes of the machine. By binding with calcium ions in the blood it prevents the process of coagulation. It is also used as an anticoagulant for laboratory testing, in that blood samples are ...
The citrate agar is green before inoculation, and turns blue, because of BTB as a positive test indicator, meaning citrate is utilized. The test is also prepared on a slant to maximize bacterial growth for an even better indication of the use of citrate.
A study in 2012 found that the maternal plasma cell-free DNA test was also able to detect trisomy 18 (Edwards syndrome) in 100% of the cases (59/59) at a false-positive rate of 0.28%, and trisomy 13 (Patau syndrome) in 91.7% of the cases (11/12) at a false-positive rate of 0.97%.
References range may vary with age, sex, race, pregnancy, [10] diet, use of prescribed or herbal drugs and stress. Reference ranges often depend on the analytical method used, for reasons such as inaccuracy , lack of standardisation , lack of certified reference material and differing antibody reactivity . [ 11 ]
The two primary methods are testing for the female pregnancy hormone (human chorionic gonadotropin (hCG)) in blood or urine using a pregnancy test kit, and scanning with ultrasonography. [1] Testing blood for hCG results in the earliest detection of pregnancy. [2] Almost all pregnant women will have a positive urine pregnancy test one week ...