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Ramesh ☆ India, 2007-10-15 12:52 (6832 d 16:36 ago) Posting: # 1189 Views: 7,441 |
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Dear group members, I have a query on Calibration curve acceptance criteria. case: We have 11 points in the calibration curve starting from STD 1 to STD 11 (lower to higher), and one blank and blank IS (blank sample with IS). In one of the subject sample analyis run, all the standards (STD 1 to STD 11) are with in the specifications for accuracy, but, both blank and blank IS are not meeting the acceptance criteria (less 20 % of the LOQ(STD 1)) against the STD 1. so we have removed the STD 1 from the regression and calculated the interference in the STD balnk and STD Zero samples (blank sample with IS), against the STD 2, making STD 2 as the new LOQ, unfortunately still both blank and blank IS are not meeting the acceptance criteria against the STD 2, at this stage we have gone further and calculated the interference against the STD 3. Making STD 3 as new LOQ, both the blank and blank IS are meeting the acceptance criteria. Shall we accept the CC curve (truncated curve) even though 2 points (consecutives) are removed form the regression, by taking in to consideration that 75 % of the CC points are included in the regression? One more problem is, we have 3 QCs with each batch [QC1(low), QC2 (medium)and QC3(high)], after making the STD 3 as new LOQ (truncated curve) the low level QC (QC1) (concentration) is falling below the STD 3 nominal concentration. Shall we accept the subject samples batch even though low level QC is falling out of the truncated CC range by repeating the unknown samples, which are below the STD 3. Please provide your valuable inputs. Regards — with regards, Ramesh |
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Helmut ★★★   Vienna, Austria, 2007-10-15 21:30 (6832 d 07:58 ago) @ Ramesh Posting: # 1192 Views: 6,340 |
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Dear Ramesh - or Debbie in PharmPK  ❝ … all the standards (STD 1 to STD 11) are with in the specifications for accuracy, but, both blank and blank IS are not meeting the acceptance criteria (less 20 % of the LOQ(STD 1)) against the STD 1. Where does this criterion (<20% of LLOQ) come from? And how do you calculate it actually - since you don't know the concentration, do you compare the measured response of the blank with the calculated response at zero (=intercept of the CC)? ❝ so we have removed the STD 1 from the regression and calculated the interference in the STD balnk and STD Zero samples (blank sample with IS), against the STD 2, making STD 2 as the new LOQ, … … in trusting the interference more than your calibrators? Most people would allow removal of data points from the calibration curve only (for <25% of data points) if the back-calculated concentration deviates more than 15% (or 20% at the LLOQ) from the nominal concentration in the following cases:
I assume, you don’t have contaminations at the other levels of the CC, because in this case you would get an increased (compared to other CCs) intercept, which should give a back-calculated value of ≪LLOQ for the blanks. Your method of defining a new LLOQ higher than than the lowest QC-level simply leads to a rejected run. Edit: Link corrected for FDA’s new site. [Helmut] — Dif-tor heh smusma 🖖🏼 Довге життя Україна! ![[image]](https://static.bebac.at/pics/Blue_and_yellow_ribbon_UA.png) Helmut Schütz ![[image]](https://static.bebac.at/img/CC by.png) The quality of responses received is directly proportional to the quality of the question asked. 🚮 Science Quotes |
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Ramesh ☆ India, 2007-10-16 06:45 (6831 d 22:43 ago) @ Helmut Posting: # 1193 Views: 6,309 |
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Dear Helmut The criteria for the < 20% of LLOQ is response at the RT of the Drug in the blank and blank+IS samples compare to the LLOQ response (STD 1). — with regards, Ramesh |
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Charl ● 2007-10-16 10:47 (6831 d 18:41 ago) @ Ramesh Posting: # 1196 Views: 6,245 |
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Dear Ramesh.. ❝ The criteria for the < 20% of LLOQ is response at the RT of the Drug in the blank and blank+IS samples compare to the LLOQ response (STD 1). I quote from FDA guidance "The analyte response at the LLOQ should be at least 5 times the rsponse compared to blank response." I understand that 100% is 4 times the 20% not 5.! are in method development or in-study analysis? once you are in in-study stage you cant just omit the Lowest concentration level LOQ. I quote from FDA guidance "At least four out of six non-zero standards should meet the above criteria, including the LLOQ and the calibration standard at the highest concentration. Excluding the standard should not change the model". at least 67% of the standards should obey the criteria for cc. regards Charl |
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H_Rotter ★ Germany, 2007-10-16 15:44 (6831 d 13:44 ago) @ Charl Posting: # 1203 Views: 6,184 |
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Hi Charl! ❝ I understand that 100% is 4 times the 20% not 5.! I would understand that 100% = 5x20%, whereas 4x20% = 80%... Hermann |
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Charl ● 2007-10-17 10:55 (6830 d 18:33 ago) @ H_Rotter Posting: # 1205 Views: 6,253 |
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Dear Hermann I always have this argument with my collegues, simple math will do the problem 20x5=100 but I always see it as: 20 (0 time), 40 ( 1 time), 60 ( 2times), 80 ( 3 times), 100 ( 4 times)...... so for me its not 20% its 16%.......  cheers..... |
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Ramesh ☆ India, 2007-10-16 07:13 (6831 d 22:15 ago) @ Helmut Posting: # 1194 Views: 6,266 |
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Dear group members, AS per the guidelines the CC standards are removed from the regression if back calculated concentration is more than the 15% of nominal concentration and 20% in case of LLOQ. CASE:
so is there any scientifica justification or any thumb rule for the removal of the CC standards. if not what will be criteria for the removal of standards if more than one is out of acceptnace criteria. with regards, Ramesh.V Edit: Post linked to another thread. [HS] — with regards, Ramesh |
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Ohlbe ★★★ France, 2007-10-18 20:36 (6829 d 08:52 ago) @ Ramesh Posting: # 1217 Views: 6,242 |
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Dear Ramesh, ❝ so is there any scientifica justification or any thumb rule for the removal of the CC standards. ❝ if not what will be criteria for the removal of standards if more than one is out of acceptnace criteria. No precision in the FDA guideline on bioanalytical method validation. The one thing to avoid, unless you want to run into trouble, would be to decide which CC to exclude based on the results of the QC samples. What I usually see is that the CC with the highest deviation is excluded first, then the calibration curve is recalculated. If other CCs are still failing, the one with the highest deviation is excluded, and so on. Your criteria should be defined in a pre-established SOP, and not on the basis of the results obtained. Regards Ohlbe |
Ing. Helmut Schütz