An enzymatic method for measuring the concentration of HDL cholesterol in the plasma portion of a whole blood-cell containing sample, wherein the sample contains HDL cholesterol as a first component and non-HDL cholesterol as a second component, where said second component interferes with the measurement of said first component if said second component is present and unblocked, said method comprising the steps of i) contacting at most 40 μL of said blood cell containing sample with a reagent mixture that dilutes the sample; ii) substantially removing blood cells to provide a substantially cell free sample containing less than 5% blood cells; iii) contacting said sample with at least one reagent selected from: I) sulfated alpha-cyclodextrins in the presence of Mg 2+; II) a synthetic polymer together with a polyanion, or a surfactant; III) an antibody to apolipoprotein B; which serves to temporarily prevent reaction of said non-HDL cholesterol second component, whereby to generate a blocked second component; iv) contacting said sample with at least one reagent mixture comprising at least one converting enzyme for cholesterol, whereby to cause the selective reaction of cholesterol to directly or indirectly generate detectable reaction products, wherein the analyte is said first component; v) monitoring said detectable reaction product or products; vi) relating an amount of said detectable product or products to the concentration of the said HDL cholesterol in said blood sample, wherein the concentration of said HDL cholesterol is related to a corresponding detectable reaction product by means of estimating an un-measurable (fictive) endpoint, by fitting an algorithm based upon a first order rate equation or a logistic function selected from: (i) Y=Y max +(Y 0 -Y max)*e^(-kX) (ii) Y = Y max - Y max *e<A>(-k(X-X 0)) (iii) Y=Y max +(Y 0 -Y max)*e^(-kX) + X*C (iv) Y = Y 0 + (Y max -Y 0)/(1+10^(logX 50 -logX)*B (v) Y=Y max +(Y 0 -Y max)/(1+X/X 50)^B (vi) Y = Y 0 +(Y max -Y 0)/(1+(X/X 50)^B (vii) Y=Y max +(Y 0 -Y max)/(1+X/X 50)^B + X*C wherein Y 0 is Y at X=0; Y max is Y at X=infinite; k is the rate constant; X 50 is X at half maximal Y; B is slope factor, steepness of slope; C is slope factor of parallel reaction; wherein step iii) may be carried out at any stage up to and including step iv) but before steps v) or vi) and wherein the reagent of step iii) may be applied to the sample separately or may be included in at least one reagent mixture of steps i) or iv). i) contacting at most 40 μL of said blood cell containing sample with a reagent mixture that dilutes the sample; ii) substantially removing blood cells to provide a substantially cell free sample containing less than 5% blood cells; iii) contacting said sample with at least one reagent selected from: I) sulfated alpha-cyclodextrins in the presence of Mg 2+; II) a synthetic polymer together with a polyanion, or a surfactant; III) an antibody to apolipoprotein B; which serves to temporarily prevent reaction of said non-HDL cholesterol second component, whereby to generate a blocked second component; I) sulfated alpha-cyclodextrins in the presence of Mg 2+; II) a synthetic polymer together with a polyanion, or a surfactant; III) an antibody to apolipoprotein B; iv) contacting said sample with at least one reagent mixture comprising at least one converting enzyme for cholesterol, whereby to cause the selective reaction of cholesterol to directly or indirectly generate detectable reaction products, wherein the analyte is said first component; v) monitoring said detectable reaction product or products; vi) relating an amount of said detectable product or products to the concentration of the said HDL cholesterol in said blood sample, wherein the concentration of said HDL cholesterol is related to a corresponding detectable reaction product by means of estimating an un-measurable (fictive) endpoint, by fitting an algorithm based upon a first order rate equation or a logistic function selected from: (i) Y=Y max +(Y 0 -Y max)*e^(-kX) (ii) Y = Y max - Y max *e<A>(-k(X-X 0)) (iii) Y=Y max +(Y 0 -Y max)*e^(-kX) + X*C (iv) Y = Y 0 + (Y max -Y 0)/(1+10^(logX 50 -logX)*B (v) Y=Y max +(Y 0 -Y max)/(1+X/X 50)^B (vi) Y = Y 0 +(Y max -Y 0)/(1+(X/X 50)^B (vii) Y=Y max +(Y 0 -Y max)/(1+X/X 50)^B + X*C wherein Y 0 is Y at X=0; Y max is Y at X=infinite; k is the rate constant; X 50 is X at half maximal Y; B is slope factor, steepness of slope; C is slope factor of parallel reaction; wherein step iii) may be carried out at any stage up to and including step iv) but before steps v) or vi) and wherein the reagent of step iii) may be applied to the sample separately or may be included in at least one reagent mixture of steps i) or iv). (i) Y=Y max +(Y 0 -Y max)*e^(-kX) (ii) Y = Y max - Y max *e<A>(-k(X-X 0)) (iii) Y=Y max +(Y 0 -Y max)*e^(-kX) + X*C (iv) Y = Y 0 + (Y max -Y 0)/(1+10^(logX 50 -logX)*B (v) Y=Y max +(Y 0 -Y max)/(1+X/X 50)^B (vi) Y = Y 0 +(Y max -Y 0)/(1+(X/X 50)^B (vii) Y=Y max +(Y 0 -Y max)/(1+X/X 50)^B + X*C