Still trying to get my head round how you ensure that you get a good, clean sample.
With HbA1c you get a blood sample at a point in time, and extrapolate back to estimate the average blood glucose concentration over the last 3 months.
It isn't clear from the article if you expect to get freshly extruded wax, or a mixture of ear wax shed over the last weeks and months.
I would assume that you might have to have your ears cleaned out at some point before you start sampling.
Edit: will add comments as I work my way through the main document linked to be the summary.
"Several glucose measurements, such as fasting and postprandial levels have been standardised, aiming to provide a predictable level of glucose concentration. However, taking these tests is often demanding for patients. Furthermore, these tests still do not accurately reflect the average concentration of glucose, which is necessary to monitor the glycemic profile in metabolic disorders [7]. Indeed, these levels are usually found either below the mean, such as those seen when fasting serum glucose (FSG) samples are taken or above that average when postprandial serum glucose (PSG) ones are used"
This does not consider the use of CGM which overcomes the objections to random sampling.
"Fasting glucose levels show stronger associations with HbA1c than postprandial glucose levels when measured in healthy people and in diabetic patients with poor glycemic control"
Interesting. Although it does leave the issue of diabetic patients with good glycemic control dangling a bit.
Ah.
"This means that HbA1c could be found within a normal range in less severe diabetic patients, who frequently have dietary transgressions. This diminishes HbA1c capacity to tightly monitor the mean glucose levels in glucose intolerance and mild diabetes. A more effective method for measuring the average concentration of glucose level should equally weight its postprandial and fasting levels across the day."
This is why time in range is more important than the average reading. See Freestyle Libre, for example.
There follows an extensive critique of all the things that HbA1c doesn't measure accurately or predict accurately. Well worth reading this bit.
I am, obviously, cynically noting that this paper is proposing something which is allegedly a better diagnostic test than HbA1c so may not be entirely impartial.
Hmmm...
"
All samples, either glycemic or HbA1c need to be taken from blood. This entails that sampling is expensive, since qualified workers, such as nurses are required. Blood samples may be associated with some side effects, such as bleeding, infection, and local pain. Nonetheless, the glycemic level is still the most requested lab test in primary health care centers in several countries [24,25]. The glycemia represents the third largest lab cost for some health systems [21]. HbA1c is also among the most demanded lab test, and it is believed that it is still unrequested [22]. More recently, real-time continuous glucose monitoring (RT-CGM) was developed to provide readings of glucose concentration variations every five minutes for up to seven days. Nonetheless, due to its high cost this approach is not available to the population at large scale. Therefore, there is a need to find not only a more reliable specimen for measuring chronic glucose concentrations over different periods but also a harmless and more economical approach.
"
Nearly all glycemic blood samples, as far as I am aware, are self test finger pricks.
Ah! Here we go!
"At baseline, in order to collect a standardized amount of earwax secretion at the time of follow-up, the right ear of enrolled participants was cleaned using the Reiner–Alexander syringe to effectively and safely remove any earwax from outer ears [41]. It is the traditional method used by clinicians for removing impacted earwax. Participants were instructed to avoid using cotton buds or the use of any other cleaning outer-ear method during the follow-up period. During the follow-up visit, participants self-cleaned their right ears using an earwax self-sampling device, according to the manufacturer instructions (www.trears.com) and the wax collected represented the previous four weeks of earwax secretion"
So the ears have to be cleaned 4 weeks prior to sampling to ensure that the ear wax is fresh and reflects the last 4 weeks. However in my reading it seems that a sample (baseline) was taken prior to the ear cleaning exercise and only the follow up was based on a pre-cleaned ear.
This next bit is where I am struggling at the moment:
"Morning blood tests were obtained at both baseline and follow up visits. The baseline blood sample was obtained after 8 h of fasting whereas the follow-up sample was taken 2 h after consuming a standardized liquid meal, 236 mL of Ensure Avance®. FSG and HbA1c levels were analyzed from baseline samples, PSG and HbA1c levels were analyzed from the follow-up samples. Chronic glucose level over the preceding one-month period was calculated using the mean between the baseline and the follow-up blood sample of glycemia. "
It looks as though they took a fasting BG reading and HbA1c for the baseline, then a postprandial BG and HbA1c for the follow up.
It appears that they then calculated the equivalent of the HbA1c by extrapolating from one fasting BG reading and one postprandial BG reading....I think.
I am not sure how accurate an estimation this is, especially as this is a very short run experiment with only two measurements, and with a small number of participants.
I would have expected the trial to run for at least 3 months with a baseline followed by 3 monthly readings, each one followed by an ear cleansing to ensure that there is only 4 weeks worth of wax in the ear at testing time.
It all seems to hinge on the acceptance that a single baseline FBG and a single PBG (I think this is the same as the FSG and PSG quoted in the paper) one month later is sufficient to establish the true chronic BG level against which to accurately measure divergence from HbA1c.
In the discussion there is a lot of propaganda against the use of CGM mainly based on cost, but it also states that monitoring is over a 7 day period, not the 14 days with a Freestyle Libre.
"The RT-CGM was lately developed to provide a glucose reading and trend levels collected every five minutes for up to seven days. Although RT-CGM may be a useful educational and motivational tool, diabetes self-management that includes the use of RT-CGM is likely to be more time-consuming for patients and force them to focus on different aspects of diabetes"
It becomes clear that the wax sample requires laboratory testing with the same cost as an HbA1c.
The "novel device" is faster in preparing the sample, because if you syringe out the ear then you have to dry the sample before analysis which takes time. The "novel device" collects a dry sample.
Further noting that if the analysis is based on a traditional analysis of a syringed sample then it must be a homogeneous sample, not stratified.
