APEX Recovery Markers

An APR is raised to many sicknesses and conditions differently in each patient. With the APEX app we can crowd-source the data from the CRP assay for any cohort of interest to you and then share the data with us for a publication or you can publish independently. A cohort of pneumonia patients, patient undergoing chemotherapy, sepsis patients in ITU all are potentially of interest and could lead to publications. The App has a price of £4.99 so that Attomarker is not sponsoring the work, simplifying the declaration of funding in the journals on publication.

The new markers are all derived from the visualisation of the acute phase response, which is in turn derived from the CRP time course. There are many other markers of the acute phase and these are part of an on-going research programme.

The APR – Acute Phase Response

The acute phase is central to the systemic response to many illnesses and tissue damage but it is rarely visualised up to now. The assumptions detailed in the Recovery Hypothesis allow the derivative of the CRP to be related to the APR and the CRP clearance from the liver. The APR function should then rise during an insult and fall during recovery, continually falling throughout an uncomplicated or perfect recovery.

APEX Recovery Markers - Figure 01

The falling trend in the APR can be used to define an uncomplicated recovery and by implication a complication. The equation will be tested with a prospective cohort study analysis. The accuracy of the serum half-life statement can be assessed based on how often the APR becomes negative; a negative APR indicates the clearance rate is over estimated; the underestimate is difficult to determine.

APEX Score

The App interpolates the CRP data and calculates the APEX score which reflects the change in the APR. Each hour the APR rises, the APEX score is incremented +1; APEX does not change if the change in CRP is less than the assay error; and APEX decreases -1 for every hour the APR is decreasing. The APEX Score rises and falls during the stay and may be near to zero on admission but this needs to be validated.

APEX Hours

The APEX hours is calculated from the APEX Score and is the total number of hours for which the APR has been rising and is a measure of the length of the acute phase event. A patient who is sick for 30 hrs (rising APR) is likely to require longer to recover and may require more frequent observations but again, this needs to be validated.

CRP 8hr-Prediction

After the first three CRP points, the App will predict the value of the CRP serum concentration based on a linear extrapolation of the APR and a numerical integration of the differential equation to include the effect of CRP clearance. This is represented as a red cross on the CRP curve with an assay accuracy spread; deviations greater than this level and a rising APEX will be indicative of complication; close to the prediction will indicate no significant change in the APR; and below the prediction will be a decreasing APR trend.

CRP Sampling Schedule

The accuracy of the APR characterisation depends on the number of CRP samples as with all data sampling; the Nyquist’s Sampling Theorem or the Nyquist-Shanon Sampling Therorem. The need to sample frequently must however be balanced with patient comfort. To capture the APR maximum from a surgical procedure a CRP sample within 12 hours of the surgery time sets a useful baseline and then morning and afternoon thereafter. Following a rising APEX, the app will predict the earliest time that a CRP sample can be taken and provide the next time at which a CRP sample will provide information about the APR and the APEX score, after an intervention for example.

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