PharmPK Discussion - Handling BLQs for NCA analysis

• On 13 Nov 2013 at 11:56:29, (Soujanya.Sunkaraneni.-a-.sunovion.com) sent the message
  

  
  Hello Everyone,
  
  I have a question about handling BLQs for a regular NCA analysis using rich plasma conc data.
  I learnt that there are methods to  handle BLQs in NONMEM for POPPK analysis (e.g. M1 to M7), but
  how do you handle BLQs in NCA analysis, especially if we have BLQs in between Tmax and Tlast?
  Even though BLQ value is not equal to 0, I feel comfortable substituting the value to 0 before Tmax
  and after Tlast (not sure if this is accurate), but how about the BLQs in between Tmax and Tlast?
  Should I
  substitute those values to 0? or
  exclude those values or assign a missing value?
  or should I impute those values with LLOQ/2?.
  Appreciate your inputs in this regard.
  
  Thanks,
  Soujanya
  
  

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• On 14 Nov 2013 at 07:39:18, Tao Liu (liutaows.aaa.gmail.com) sent the message
  

  
  Hi Soujanya,
  
  First, I agree with your BQL rule befure Tmax. For BLLOQ data after Tmax, normally MISSING (OR ND)
  will be used. In most of the situation, it should not influence your terminal phase slope estimation
  if you have proper sampling time points. Sometimes, LLOQ/2 (OR LLOQ/3) might be used for the first
  BLLOQ data after Tmax and Missing for the following BLLOQ data. To me, it is difficult to tell why
  you select LLOQ/2 not LLOQ/3, vise versa. So, I prefer to using Missing for all BLLOQ data after
  Tmax. However, you should also use your judgement  sometime and compare CT curves between different
  subjects because of irregular concentration time curve, especially when the concentration is nearby
  LLOQ.
  
  Tao Liu BSc
  PhD Student
  
  Center for Translational Medicine
  University of Maryland, Baltimore
  http://www.ctm.umaryland.edu/
  
  Email: liutaows.aaa.gmail.com
  
  

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