An analysis method for a real-time nucleic acid amplification reaction RNR, the method comprising: - acquiring an intensity of a fluorescence emission of an analyte for each amplification reaction cycle of the RNR; - creating a growth curve indicative of the intensity of the fluorescence emission over a RNR cycle range, - calculating a combined threshold function over the RNR cycle range comprising at least two different threshold levels, wherein the combined threshold function is dependent on the cycle number of the RNR, the combined threshold function transitioning from an initial threshold level to a final threshold level, the initial threshold level being different than the final threshold level, the final threshold level being B + r x I, wherein B is a baseline function, the baseline being the initial portion of the growth curve which shows no signal increase, r is a positive percentage parameter, and I is an intercept extrapolation to cycle number 0, the initial threshold level being - y ( x) = B + p · G = B + p · ( S - B), wherein B is the baseline function, S is the saturation line of the growth curve, G is the growth from the baseline to the saturation line, and p is a parameter between 0% and 100%, wherein the initial threshold level is above the final threshold level, wherein the combined threshold function is selected from a group of three functions comprising: i. a CTF with a linear transition from the initial threshold level (y 1) to the final threshold level (y 2) according to: CTF x = y 1 + y 2 − y 1 ⋅ x − x 1 x 2 − x 1, where x1 is an early reaction cycle number equal to 0 or 1, x2 is a late reaction cycle number larger than 30, y1 is the initial threshold level, y2 is the final threshold level. ii. a CTF with a polynomial transition from the initial threshold level (y 1) to the final threshold level (y 2) according to: CTF x = y 1 + y 2 − y 1 ⋅ x − x 1 x 2 − x 1 p, where p is a fixed polynomial order, wherein p is 2 for a quadratic polynomial function; iii. a CTF with an exponential transition from the initial threshold level (y 1) to the final threshold level (y 2) according to CTF x = e x 2 ⋅ ln y 1 − x 1 ⋅ ln y 2 x 2 − x 1 ⋅ y 2 y 1 x x 2 − x 1; - determining a quantification cycle number (Cq) of the RNR, the quantification cycle number (Cq) being indicative of a quantitative and/or qualitative analysis result of the growth curve as the cycle number corresponding to an intersection of the growth curve with the combined threshold function. - acquiring an intensity of a fluorescence emission of an analyte for each amplification reaction cycle of the RNR; - creating a growth curve indicative of the intensity of the fluorescence emission over a RNR cycle range, - calculating a combined threshold function over the RNR cycle range comprising at least two different threshold levels, wherein the combined threshold function is dependent on the cycle number of the RNR, the combined threshold function transitioning from an initial threshold level to a final threshold level, the initial threshold level being different than the final threshold level, the final threshold level being B + r x I, wherein B is a baseline function, the baseline being the initial portion of the growth curve which shows no signal increase, r is a positive percentage parameter, and I is an intercept extrapolation to cycle number 0, the initial threshold level being - y ( x) = B + p · G = B + p · ( S - B), wherein B is the baseline function, S is the saturation line of the growth curve, G is the growth from the baseline to the saturation line, and p is a parameter between 0% and 100%, wherein the initial threshold level is above the final threshold level, wherein the combined threshold function is selected from a group of three functions comprising: i. a CTF with a linear transition from the initial threshold level (y 1) to the final threshold level (y 2) according to: CTF x = y 1 + y 2 − y 1 ⋅ x − x 1 x 2 − x 1, where x1 is an early reaction cycle number equal to 0 or 1, x2 is a late reaction cycle number larger than 30, y1 is the initial threshold level, y2 is the final threshold level. ii. a CTF with a polynomial transition from the initial threshold level (y 1) to the final threshold level (y 2) according to: CTF x = y 1 + y 2 − y 1 ⋅ x − x 1 x 2 − x 1 p, where p is a fixed polynomial order, wherein p is 2 for a quadratic polynomial function; iii. a CTF with an exponential transition from the initial threshold level (y 1) to the final threshold level (y 2) according to CTF x = e x 2 ⋅ ln y 1 − x 1 ⋅ ln y 2 x 2 − x 1 ⋅ y 2 y 1 x x 2 − x 1; i. a CTF with a linear transition from the initial threshold level (y 1) to the final threshold level (y 2) according to: CTF x = y 1 + y 2 − y 1 ⋅ x − x 1 x 2 − x 1, where x1 is an early reaction cycle number equal to 0 or 1, x2 is a late reaction cycle number larger than 30, y1 is the initial threshold level, y2 is the final threshold level. ii. a CTF with a polynomial transition from the initial threshold level (y 1) to the final threshold level (y 2) according to: CTF x = y 1 + y 2 − y 1 ⋅ x − x 1 x 2 − x 1 p, where p is a fixed polynomial order, wherein p is 2 for a quadratic polynomial function; iii. a CTF with an exponential transition from the initial threshold level (y 1) to the final threshold level (y 2) according to CTF x = e x 2 ⋅ ln y 1 − x 1 ⋅ ln y 2 x 2 − x 1 ⋅ y 2 y 1 x x 2 − x 1; - determining a quantification cycle number (Cq) of the RNR, the quantification cycle number (Cq) being indicative of a quantitative and/or qualitative analysis result of the growth curve as the cycle number corresponding to an intersection of the growth curve with the combined threshold function.