TABLE 2.
POTENTIAL SOURCES OF NASAL POTENTIAL DIFFERENCE VARIABILITY IN MULTICENTER TRIALS
| Procedural |
| Operator skill |
| Electrode measurement device |
| Placement of measuring electrode |
| Movement artifact |
| Temperature |
| Solution content (ion concentrations, pH, tonicity) |
| Data capture and scoring |
| Altitude/study environment |
| Biological |
| In vivo CFTR activity based on mutation class |
| Modifier genes influencing ion transport |
| Nasal mucosal integrity |
| Nasal anatomy |
| Concomitant medications |
| Exercise |
| Treatment |
| Differential biological effects |
| Metabolic differences |
| Compliance |
| Analysis method |
| Mean nostril measurements |
| Single measurements (i.e., most polarizing TCS response per subject, individual nostril analysis) |
| Sodium transport |
| Mean basal PD |
| Most polarizing basal PD |
| Post–Ringer's basal PD |
| Amiloride-sensitive PD |
| Chloride transport |
| ΔPD after zero chloride perfusion |
| ΔPD after β2-adrenergic receptor agonist perfusion |
| Total CFTR-dependent Cl− secretion |
| ΔPD after ATP perfusion |
Definition of abbreviations: ΔPD = change in potential difference; TCS = total chloride secretion.