Actually u have misunderstood the concept... Know some facts about this which will clear ur doubts...

1) TC is total count or the number of WBCs/ white blood cells per cubic mm of blood

2) DC is differential count, which expresses the configuration or contitution of the WBCs in the blood like.. There are 5 different types of WBCs ----> Neutrophils, Eosinophils, Basophils, Lymphocytes, Monocytes.. The composition is expressed in terms of percentage like N60%, L35%, E3%, M2%, B0%... This is DC

3) Both the tests require just a drop of blood.. Actually any blood test when done as a single test requires just a drop of blood.. But when asked in a bulk, we have to draw the blood from the vein..

4) There is nothing like, the TC, DC should be done in the finger prick blood and Others in the venous blood.. All the tests can be done in either way.. Unless there are certain exceptions where we require a large amount of blood which cannot be done with finger pricked blood...

5) Just a little more about TC and DC. For DC, its done after preparing a blood smear on a slide, which requires just a small drop of blood.. If excess is taken it cannot be done...

And Tc, now in most of the labs, automated counters are available which just takes a few miclo litres of blood for estimation

Hope u are clarified of ur doubt...

History The alkaline fermentation of urine (urea) with the resultant production of ammonia was hypothesized to occur due to the action of microorganisms by Reoch in 1875 (6). Many forms of urea-degrading bacteria were subsequently isolated and their urease activity studied (3). Urease activity is considered to be a major criterion for the identification of Proteus species and allows for Proteus to be distinguished from non-lactose-fermenting members of the Enterobacteriaceae (1). A chemically defined medium that was shown to be differential for Proteus species was formulated by Stuart (7).  In this medium, Proteus are capable of using urea as a sole nitrogen source and produce sufficient quantities of ammonia to overcome the high buffering capacity of the medium resulting in a color change from yellow to bright pink (fuschia). Christensen later formulated a medium that would allow growth of other members of the Enterobacteriaceae that cannot utilize the by-product of urea hydrolysis (ammonia) as a sole nitrogen source for growth (2). This medium also has a decreased buffering capacity allowing for the detection of smaller quantities of alkali produced from the degradation of urea. Thus organisms with a slight or delayed urease activity can be detected with Christensen’s urea agar. Purpose The urease test identifies those organisms that are capable of hydrolyzing urea to produce ammonia and carbon dioxide. It is primarily used to distinguish urease-positive Proteeae from other Enterobacteriaceae. Theory (5, 8) Urease is a constitutively expressed enzyme that hydrolyzes urea to carbon dioxide and ammonia. (NH2)2CO + H2O → CO2 + 2NH3 Urease test media contain 2% urea and phenol red as a pH indicator. An increase in pH due to the production of ammonia results in a color change from yellow (pH 6.8) to bright pink (pH 8.2). Urea broth (Stuart’s urea broth) is a highly buffered medium requiring large quantities of ammonia to raise the pH above 8.0 resulting in a color change. This medium provides all essential nutrients for Proteus, for which it is differential. Urea agar (Christensen’s urea agar) has a reduced buffer content and contains peptones and glucose. This medium supports the growth of many enterobacteria allowing for the observation of urease activity. RECIPE Two media types are commonly used to detect urease activity. Christensen’s urea agar is used to detect urease activity in a variety of microorganisms. Stuart’s urea broth is used primarily for the differentiation of Proteus species. Both media types are available commercially as prepared tubes or as a powder. Christensen’s Urea Agar (2, 4, 5)   Ingredient   Amount Peptone  1 g Dextrose  1 g Sodium chloride   5 g Potassium phosphate, monobasic  2 g Urea   20 g Phenol red   0.012 g Agar 15 to 20 g To prepare the urea base, dissolve the first six ingredients in 100 ml of distilled water and filter sterilize (0.45-mm pore size). Suspend the agar in 900 ml of distilled water, boil to dissolve completely, and autoclave at 121oC and 15 psi for 15 minutes. Cool the agar to 50 to 55oC. Aseptically add 100 ml of filter-sterilized urea base to the cooled agar solution and mix thoroughly. Distribute 4 to 5 ml per sterile tube (13 x 100 mm) and slant the tubes during cooling until solidified. It is desirable to have a long slant and short butt. Prepared media will have a yellow-orange color. Store the prepared media in the refrigerator at 4 to 8oC until needed. Once prepared, do not reheat the medium as the urea will decompose. Stuart’s Urea Broth (4, 5, 7)   Ingredient   Amount Yeast extract  0.1 g Potassium phosphate, monobasic  9.1 g Potassium phosphate, dibasic  9.5 g Urea 20 g Phenol red    0.01 g   Dissolve all ingredients in 1 liter of distilled water and filter sterilize (0.45-mm pore size). Distribute 3 ml of prepared broth per sterile tube (13 x 100 mm). Prepared media will have a yellow-orange color. Store the prepared broth in the refrigerator at 4 to 8oC until needed. Do not heat the medium as the urea will decompose. PROTOCOL Christensen’s Urea Agar (4, 5) Use a heavy inoculum from an 18- to 24-hour pure culture to streak the entire slant surface. Do not stab the butt as it will serve as a color control (Fig. 1c). Incubate tubes with loosened caps at 35oC. Observe the slant for a color change at 6 hours, 24 hours, and every day for up to 6 days. Urease production is indicated by a bright pink (fuchsia) color on the slant that may extend into the butt. Note that any degree of pink is considered a positive reaction. Prolonged incubation may result in a false-positive test due to hydrolysis of proteins in the medium. To eliminate protein hydrolysis as the cause of a positive test, a control medium lacking urea should be used. Rapidly urease-positive Proteeae (Proteus spp., Morganella morganii, and some Providencia stuartii strains) will produce a strong positive reaction within 1 to 6 hours of incubation. Delayed-positive organisms (e.g., Klebsiella or Enterobacter) will typically produce a weak positive reaction on the slant after 6 hours, but the reaction will intensify and spread to the butt on prolonged incubation (up to 6 days). The culture medium will remain a yellowish color if the organism is urease negative (Fig. 1).        a                    b                     c                    d       FIG. 1. Urea agar test results. Urea agar slants were inoculated as follows: (a) uninoculated, (b) Proteus mirabilis (rapidly urease positive), (c) Klebsiella pneumoniae (delayed urease positive), (d) Escherichia coli (urease negative). All samples were incubated at 37oC for 16 hours. Stuart’s Urea Broth (4, 5) Use a heavy inoculum from an 18- to 24-hour pure culture to inoculate the broth. Shake the tube gently to suspend the bacteria. Incubate tubes with loosened caps at 35oC. Observe the broth for a color change at 8, 12, 24, and 48 hours. Urease production is indicated by a bright pink (fuchsia) color throughout the broth. Rapidly urease-positive Proteeae (Proteus spp., Morganella morganii, and some Providencia stuartii strains) for which this medium is differential, will produce a strong positive reaction as early as 8 hours, but always within 48 hours of incubation. Delayed-positive organisms (e.g., Enterobacter) will not produce a positive reaction due to the high buffering capacity of this medium.                                  a                        b

VDRL is a blood test that is used to determine whether or not you have an active syphilis infection. Although a positive test usually means that you have syphilis, the fact that VDRL looks for antibodies to a non-syphilis specific protein called cardiolipin does mean there can be false positives. False positives occur in 1 to 2 percent of the population and can be caused by many conditions including pregnancy, HIV infection, tuberculosis and certain other bacterial infections.
A VDRL test can be used to detect new syphilis infections or follow the course of syphilis treatment, since the levels of anti-cardiolipin antibodies in the blood will change depending on how active a syphilis infection is in the body. Over the long term, latent syphilis infections can, however, lead to false negative tests. RPR is another non-specific test for syphilis that is used in similar ways, and both RPR and VDRL are known as nontreponemal tests.

There are also tests for syphilis that look specifically for antibodies to the organism that causes the disease - Treponema pallidum. These treponemal tests are somewhat less likely to cause a false positive diagnosis, but can remain positive even after an infection has been cured. They only determine that a person has been infected with syphilis at some point in the past, not whether or not they are currently infected.

It is important to know that VDRL is only designed to be used as a test for syphilis. If you are concerned you may have HIV or another STD, you will need to be tested for those diseases separately.