Summary Statistics
Copy for LLM
Copy page as Markdown for LLMs
View as Markdown
Open this page as Markdown
Open in ChatGPT
Get insights from ChatGPT
Open in Claude
Get insights from Claude

Overview

Tidepool Platform automatically calculates several summary statistics for each user as they upload diabetes data into their account. Currently supported data types are CGM and BGM, from Continuous Glucose Monitors and Blood Glucose Meters, respectively. Our plan is to add insulin delivery summaries as well in the future.

The following diagram illustrates how the overall process works using manual Tidepool Uploader upload as an example. The same process applies regardless of how the data arrives in the user's account. Other examples are automatically uploading using Tidepool Mobile, or via cloud-to-cloud import from Dexcom Clarity or Abbott LibreView, or even 3rd party applications such as xDrip.

NOTE: The summary calculation itself is nearly instantaneous. However, it is triggered by the arrival of new data so depending on the path of the upload it may take anywhere from few minutes to several hours for the summary statistics to be recalculated.

Calculation

The summary calculation is done in batches of up to 250 most out-of-date user accounts, up to 4 batches in one iteration, where each iteration may begin every 30 seconds. Thus, each calculation iteration may update up to 1,000 accounts. The calculation for each user proceeds as shown in the diagram below:

Each user's data is first summarized into a set of 1-hour buckets separated by type (CGM or BGM) over the last 60 days, for a maximum of 1,440 buckets per type. The 60 day window is backwards from the date of the last uploaded data for each user, not the current date. The window may be shorter than 60 days of data if the user has not uploaded enough data. The window may also contain gaps.

The 1-hour buckets are then further summarized by type (CGM, BGM) into 1, 7, 14, and 30 day periods again backwards from the date of last uploaded data. In each period record, there is a delta record from the previous period of the corresponding duration. This enables period-over-period comparisons to support advanced dashboards such as Stanford Timely Interventions for Diabetes Excellence or TIDE (paper). The following diagram illustrates the relationship of the periods and the corresponding delta record.

Thus, a user who has both CGM and BGM data may have up to the following number of summary calculation artifacts:

\begin{aligned} [\begin{matrix} CGM \\ BGM \end{matrix}] types \times 60 days \times 24 hours & = 2,880 hourly buckets \\ [\begin{matrix} CGM \\ BGM \end{matrix}] types \times [\begin{matrix} 1 & 7 & 14 & 30 \end{matrix}] days & = 8 periods \end{aligned}

All of the summary period data is stored within each user account to enable quick sorting and filtering in each clinic's patient list. If a user is a patient of multiple clinics, all clinics share the same summary data.

Threshold Values

The summary calculation uses the glycemic targets established by ADA standards of care and AACE (paper, table) to characterize each CGM or BGM glucose sample. The same target ranges are currently used for all users, and not personalized based on the user's diagnosis type or either the user's or the clinic's preferences. The glycemic target ranges are listed in the table below. In addition to the discrete ranges, we also define two additional composite ranges AnyLow and AnyHigh. Note also that the VeryHigh range is inclusive of the ExtremeHigh range.

Unit	AnyLow		Target	AnyHigh
Unit	VeryLow	Low	Target	High	VeryHigh	ExtremeHigh
mmol/L	v < 3.0	3.0 ≤ v < 3.9	3.9 ≤ v ≤ 10.0	10.0 < v ≤ 13.9	v > 13.9	v ≥ 19.4
mg/dL	v < 54	54 ≤ v < 70	70 ≤ v ≤ 180	180 < v ≤ 250	v > 250	v ≥ 350

NOTE: Tidepool normalizes glucose samples to mmol/L units. If the original sample was in mg/dL units, it is converted using a conversion factor of 18.01559 derived from the molecular weight of glucose (C₆H₁₂O₆):

12.01070 \frac{g}{mol} \times 6 + 1.00794 \frac{g}{mol} \times 12 + 15.99940 \frac{g}{mol} \times 6 = 180.1559 \frac{g}{mol}

Hourly Bucket Data Fields

Each bucket has a set of common fields, as well as a set of fields repeated for each of the 7 named summary ranges: InLow, InTarget, InHigh, InVeryHigh, InExtremeHigh, InAnyLow, and InAnyHigh. For brevity, in the following table the placeholder Xxx corresponds to those names rather than repeating each set of fields.

GlucoseBucket

CGM	BGM	Field	Type	Unit	Notes
✅	✅	Type	string		Type of data in this bucket: `cgm` or `bgm`
✅	✅	Date	date		Start time of the bucket
✅	✅	LastRecordTime	date		Time of the last sample in the bucket
✅		LastRecordDuration	int	min	Duration of the last sample in the bucket
✅	✅	Total.Glucose	float	mmol/L	Sum of all samples in the bucket
✅		Total.Minutes	int	min	Sum of minutes covered by all samples in the bucket
✅	✅	Total.Records	int		Count of all samples in the bucket
✅	✅	Xxx.Glucose	float	mmol/L	Sum of all samples within the thresholds of Xxx in the bucket
✅		Xxx.Minutes	int	min	Sum of minutes covered by each sample within the thresholds of Xxx in the bucket
✅	✅	Xxx.Records	int		Count of samples within the thresholds of Xxx in the bucket

Summary Period Data Fields

GlucosePeriod.GlucoseManagementIndicator is only present if GlucosePeriod.Total.Percent > 70
- It is calculated using the Jaeb formula to produce a GMI value in mmol/mol units, and then using the NGSP formula to produce a % HbA1c value
- It is rounded to one decimal point of precision
GlucosePeriod.Delta is not recursive: it is only present in the top-level GlucosePeriod
GlucosePeriod.Total is always present, but the threshold ranges are present only if:
- GlucosePeriod.DaysInPeriod ≤ 1 and GlucosePeriod.Total.Percent > 70 or
- GlucosePeriod.DaysInPeriod > 1 and GlucosePeriod.Total.Minutes > 1,440 (=24 hours)
GlucoseRange.Variance is only present in GlucosePeriod.Total

GlucosePeriod

CGM	BGM	Field	Type	Unit	Notes
✅	✅	Type	string		Type of data in this period: `cgm` or `bgm`
✅	✅	DaysInPeriod	int		Number of days in this period: 1, 7, 14, or 30
✅	✅	DaysWithData	int		Number of days where Total.Records > 0
✅	✅	HoursWithData	int		Number of hours where Total.Records > 0
✅	✅	Total	GlucoseRange		Totals for all samples regardless of thresholds
✅	✅	InVeryLow	GlucoseRange
✅	✅	InLow	GlucoseRange
✅	✅	InTarget	GlucoseRange
✅	✅	InHigh	GlucoseRange
✅	✅	InVeryHigh	GlucoseRange
✅	✅	InExtremeHigh	GlucoseRange
✅	✅	InAnyLow	GlucoseRange		InVeryLow + InLow
✅	✅	InAnyHigh	GlucoseRange		InHigh + InVeryHigh (this includes InExtremeHigh)
✅	✅	AverageDailyRecords	float		$\frac{Total.Records}{DaysInPeriod}$
✅	✅	AverageGlucoseMmol	float	mmol/L	$\frac{Total.Glucose}{Total.Records}$
✅		GlucoseManagementIndicator	float	% HbA1c	$(12.71 + 4.70587 \times AverageGlucose) \times 0.09148 + 2.152$
✅		StandardDeviation	float	mmol/L	$\sqrt{\frac{Total.Variance}{Total.Minutes}}$
✅		CoefficientOfVariation	float		$\frac{StandardDeviation}{AverageGlucoseMmol}$
✅	✅	Delta	GlucosePeriod		Deltas from the previous period of the same duration

GlucoseRange

CGM	BGM	Field	Type	Unit	Notes
✅	✅	Glucose	float	mmol/L	Sum of all samples in the period
✅		Minutes	int	min	Sum of minutes covered by each sample in the period
✅	✅	Records	int		Count of samples in the period
✅	✅	Percent	float	%	if $Total . Minutes \neq 0$ : $\frac{Xxx . Minutes}{Total . Minutes}$ or if $Total . Records \neq 0$ : $\frac{Xxx . Records}{Total . Records}$
✅		Variance	float	${(\frac{mmol}{L})}^{2}$
Calculated using weighted incremental algorithm.

Handling Multiple Data Sources

In the event there are multiple CGM devices uploading data to the user's account, the initial 1-hour bucketing skips any excess data samples within a blackout window defined relative to each data sample that is included in the bucket. Put another way, each data sample included in the bucket masks any following excess data points until the blackout window expires.

In the following example there is a series of data samples in the current 1-hour bucket coming from a Dexcom G6 CGM which measures CGM every 5 minutes, and another hypotethical CGM device that provides data samples at 1 minute intervals.

Time	Device	Action
xx:00:00	Dexcom G6	Included in calculation. Sets blackout window to 5 minutes.
xx:00:30	Brand X	Ignored within blackout window.
xx:01:30	Brand X	Ignored within blackout window.
xx:02:30	Brand X	Ignored within blackout window.
xx:03:30	Brand X	Ignored within blackout window.
xx:04:30	Brand X	Ignored within blackout window.
xx:05:00	Dexcom G6	Included in calculation. Resets the blackout window to 5 minutes.
xx:05:30	Brand X	Ignored within blackout window.
xx:06:30	Brand X	Ignored within blackout window.
...	...	...

The blackout windows are defined as 15 minutes for Abbott FreeStyle Libre devices, and 5 minutes for all other devices.

Summary StatisticsCopyCopy for LLMCopy page as Markdown for LLMsView as MarkdownOpen this page as MarkdownOpen in ChatGPTGet insights from ChatGPTOpen in ClaudeGet insights from Claude