Enzyme Chemistry: GOx vs. GDH

Enzyme Chemistry: GOx vs. GDH

Blood glucose test strips use an enzyme to react with the glucose in a drop of blood. The two main enzyme families are glucose oxidase (GOx) and glucose dehydrogenase (GDH), and choosing between them comes down to two problems: oxygen and other sugars [2].

GOx is the more selective enzyme. When FDA warned in 2009 about strips that misread other sugars as glucose, it named glucose oxidase among the methods those sugars don't affect [1]. Its weak spot is oxygen. On the strip, oxygen in the blood competes with the mediator (the chemical that carries electrons from the enzyme to the electrode) for electrons from GOx [2]. GOx strips are generally calibrated for fingertip capillary blood. Extra oxygen pushes readings falsely low, which is why arterial blood and blood from someone using supplemental oxygen are a problem. Too little oxygen pushes them falsely high; venous blood and blood from someone with severe COPD both carry less [2]. In a high-altitude study described in the same review, GOx meters including the OneTouch Ultra read 6% to 15% high, and the GDH meters were more accurate [2].

GDH strips are less affected by oxygen, but GDH is a less specific enzyme: other sugars such as maltose can compete with glucose for it [2]. Oxygen tolerance also doesn't mean a strip is approved for any blood sample. That depends on its labeling. The GDH-NAD FreeStyle Precision Neo strip, for example, is labeled as not designed for use with arterial or venous blood [5].

The sugar problem was worst with GDH-PQQ, GDH paired with the cofactor pyrroloquinoline quinone. In an August 13, 2009 notice, FDA said GDH-PQQ strips cannot tell glucose from maltose, xylose or galactose, which appear in some drugs and biologics and in Extraneal (icodextrin) peritoneal dialysis solution [1]. FDA had received 13 reports of death from 1997 to 2009 in which documented sugar interference caused falsely high GDH-PQQ readings, and all of those deaths happened in healthcare facilities [1]. The same notice listed GDH-NAD and GDH-FAD, along with glucose oxidase, as unaffected [1].

Many strips did move to GDH-FAD (GDH with the cofactor flavin adenine dinucleotide). FDA's decision summaries list it for the OneTouch Verio system (cleared in 2011) and the Accu-Chek Guide (cleared in 2016) [9][8]. As of October 2026, though, the US market still carries every family. LifeScan still lists OneTouch Ultra test strips [7], a glucose oxidase design according to the 2009 review [2]. FDA cleared the glucose oxidase Prodigy Astro in 2016 [6]. FreeStyle Precision Neo strips use GDH-NAD [5]. Roche's Accu-Chek Aviva Plus strips, cleared in 2011, use a mutant GDH-PQQ, an engineered variant of the enzyme [3]. Roche says those strips will stay available even though the Aviva meter has been discontinued [4], and their FDA decision summary still notes that galactose above 15 mg/dL in the blood causes overestimated results [3].

Here's what surprised us: no enzyme fully escapes sugar interference. Even the glucose oxidase Prodigy Astro's FDA decision summary warns against using it during or after a xylose absorption test [6]. The summaries for the GDH-FAD Accu-Chek Guide and OneTouch Verio [8][9] and the GDH-NAD Precision Neo [5] carry similar xylose warnings. If you receive treatments that contain other sugars, which strip fits your situation is a question for your care team.