aptamer-based electrochemical sensor for the screening of pulmonary TB among
presumptive TB subjects. The development of the sensor was guided by target
product profiles (TPPs) demarcated by the WHO for community-based triage or
referral testing (TPP #2), namely, swift, facile, and specific and can be performed at
the primary healthcare center (microscopy center level). The test costed around
$1–3/test and yields ~92.3% sensitivity (95% CI 64–100%) and ~91.2% specificity
(95% CI 80.7–97%) in just 30 min [18].
3.2 TPP for Point-Of-Care (POC) Tests
In order to improve the management of POC testing, Pai et al. have highlighted the
importance of defining the diversity of target product profiles, particularly in
resource-limited settings [17]. Five TPP settings that are useful at different levels
are TPP1 for homes, TPP2 for communities, TPP3 for clinics, TPP4 for peripheral
laboratories, and TPP5 for hospitals (Fig. 1). Oral fluid-based HIV tests or lateral
flow assay devices are a few examples that span the entire spectrum of TPPs that can
be performed in home- to hospital-based settings. On the other hand, techniques such
as ELISA, aptamer-linked immunosorbent assay (ALISA), and microscopy can only
be performed by trained and qualified personnel, thus limiting the technology to
laboratories and hospitals [19]. Each of the abovementioned settings has individual
set of challenges for diagnosis monitoring, and treatment of a disease, and challenges
can vary from country to country, within the country, and urban versus rural
demographics. Furthermore, barriers could be economical and infrastructural, such
as unaffordability of instruments at home or community level, frequent power
outrage, and lack of adequate storage space or temperature control. It could also
be due to supply chain deficiencies or lack of qualified and trained personnel and
healthcare workers in low-resource countries.
With no TPP in place for aptamer research and promising potential of aptamers in
diagnostics and therapeutics, Tarun and colleagues adopted the abovementioned
TPP model to reduce the “bench-to-bedside” translation of aptamer technology
[5, 20–22] (Fig. 2). Diagnostic assays such as aptamer-linked immunosorbent
assay (ALISA), dot blot, and apta-PCR that are used for the detection of Rickettsia
and food pathogens were positioned in laboratory and hospitals settings, as these
assays required qualified and trained personnel along with the instrument to perform
the diagnostics. On the other hand, assays equipped with handheld devices, such as
fluorescence-based assays and vitamin D detection, were placed at community and
clinical levels. The categorization of these diagnostic assays into different settings
beforehand would not help to speed up the translation process but would also
eliminate unnecessary steps and effort required for the development and validation
of the assays, thereby bringing the product a step closer to the end user. Considering
the wide success and affordability of the personal glucose meter (PGM) in improving and saving the lives of diabetic patients, Liu et al. developed a novel technology
by conjugating functional DNA molecules to invertase enzyme for the detection of
Defining Target Product Profiles (TPPs) for Aptamer-Based Diagnostics
203
presumptive TB subjects. The development of the sensor was guided by target
product profiles (TPPs) demarcated by the WHO for community-based triage or
referral testing (TPP #2), namely, swift, facile, and specific and can be performed at
the primary healthcare center (microscopy center level). The test costed around
$1–3/test and yields ~92.3% sensitivity (95% CI 64–100%) and ~91.2% specificity
(95% CI 80.7–97%) in just 30 min [18].
3.2 TPP for Point-Of-Care (POC) Tests
In order to improve the management of POC testing, Pai et al. have highlighted the
importance of defining the diversity of target product profiles, particularly in
resource-limited settings [17]. Five TPP settings that are useful at different levels
are TPP1 for homes, TPP2 for communities, TPP3 for clinics, TPP4 for peripheral
laboratories, and TPP5 for hospitals (Fig. 1). Oral fluid-based HIV tests or lateral
flow assay devices are a few examples that span the entire spectrum of TPPs that can
be performed in home- to hospital-based settings. On the other hand, techniques such
as ELISA, aptamer-linked immunosorbent assay (ALISA), and microscopy can only
be performed by trained and qualified personnel, thus limiting the technology to
laboratories and hospitals [19]. Each of the abovementioned settings has individual
set of challenges for diagnosis monitoring, and treatment of a disease, and challenges
can vary from country to country, within the country, and urban versus rural
demographics. Furthermore, barriers could be economical and infrastructural, such
as unaffordability of instruments at home or community level, frequent power
outrage, and lack of adequate storage space or temperature control. It could also
be due to supply chain deficiencies or lack of qualified and trained personnel and
healthcare workers in low-resource countries.
With no TPP in place for aptamer research and promising potential of aptamers in
diagnostics and therapeutics, Tarun and colleagues adopted the abovementioned
TPP model to reduce the “bench-to-bedside” translation of aptamer technology
[5, 20–22] (Fig. 2). Diagnostic assays such as aptamer-linked immunosorbent
assay (ALISA), dot blot, and apta-PCR that are used for the detection of Rickettsia
and food pathogens were positioned in laboratory and hospitals settings, as these
assays required qualified and trained personnel along with the instrument to perform
the diagnostics. On the other hand, assays equipped with handheld devices, such as
fluorescence-based assays and vitamin D detection, were placed at community and
clinical levels. The categorization of these diagnostic assays into different settings
beforehand would not help to speed up the translation process but would also
eliminate unnecessary steps and effort required for the development and validation
of the assays, thereby bringing the product a step closer to the end user. Considering
the wide success and affordability of the personal glucose meter (PGM) in improving and saving the lives of diabetic patients, Liu et al. developed a novel technology
by conjugating functional DNA molecules to invertase enzyme for the detection of
Defining Target Product Profiles (TPPs) for Aptamer-Based Diagnostics
203