Health practice questions.

In February 2021 the United States Food and Drug Administration warned that pulse oximeters can overestimate blood oxygen saturation in patients with darker skin. Where does that discrepancy originate?

• In the software that averages the readings over a ten-second window
• In the optical measurement, because pigmentation absorbs some of the light used
• In the hospital record system, which stores the reading without any timestamp attached
• In the patient's decision about when to place the device on the finger

Answer: In the optical measurement, because pigmentation absorbs some of the light used

The device infers saturation from how much light of two wavelengths passes through tissue, and melanin absorbs part of that light, so the bias sits in the physical measurement and the population the device was calibrated on rather than in any code. A clinician who trusts the displayed number can therefore miss low oxygen levels in exactly the patients most at risk.

Germany's Corona-Warn-App, released in June 2020, matched exposures on the user's own phone, while Singapore's TraceTogether, released in March 2020, uploaded contact records to a central government server. In January 2021 the Singapore government confirmed that police could access TraceTogether records under existing criminal procedure law. Which design property best explains that difference in outcome?

• Where records are held decides who can be compelled to disclose them
• Bluetooth signal strength is measured more accurately by a central server
• Decentralised designs encrypt their contact records while centralised designs do not
• A centralised design allows more people to install the application at once

Answer: Where records are held decides who can be compelled to disclose them

A decentralised design leaves nothing central to seize, so the question of compelled disclosure never arises; the Singapore case showed that a purpose announced at launch does not override other laws already on the statute book. Both systems used encryption, which is why storage location rather than cryptography is the deciding property.

In 2023 the United States Federal Trade Commission ordered an online counselling service to pay 7.8 million dollars after it shared clients' email addresses and intake questionnaire answers with advertising platforms. Which feature of the arrangement allowed data of that sensitivity to be shared at all?

• The clients had each waived their statutory rights by paying with a credit card
• The advertising platforms were located outside the United States
• The questionnaire answers had been anonymised before they were sent
• The service was not a covered entity under the health privacy law of 1996

Answer: The service was not a covered entity under the health privacy law of 1996

The 1996 health privacy law binds providers, health plans and clearing houses together with their business associates, so a consumer service collecting the same kind of information can sit outside it. The gap is jurisdictional rather than technical, which is why the regulator acted on misleading privacy promises instead of on health law.

A hospital advertises 'robotic surgery' performed with a da Vinci system, first cleared by the United States regulator in 2000. The instruments move only while a surgeon at a console moves the controls. Which description of the system is accurate?

• It is an autonomous system that plans and executes the operation itself
• It is a rule-based expert system that selects the operation from a stored database
• It is teleoperated, so responsibility for each movement stays with the surgeon
• It is a machine learning system trained on recordings of previous operations

Answer: It is teleoperated, so responsibility for each movement stays with the surgeon

Automation is a spectrum, and this point on it steadies and scales the surgeon's hands rather than replacing the decision, so the chain of accountability is unchanged even though the marketing word suggests otherwise. Mistaking remote control for autonomy is the same error as calling a driver-assistance feature self-driving.

A smartwatch feature that screens for irregular heart rhythm is worn by millions of mostly young, healthy people. Even though the feature rarely flags a healthy wearer, most of the alerts it produces in that population are not confirmed by follow-up testing. Which explanation fits?

• The condition is rare in the group, so false alerts outnumber true ones
• The optical sensor cannot record any signal while the wearer is moving
• The watch is not permitted to store data for longer than twenty-four hours
• The follow-up test is less accurate than the screening feature it checks

Answer: The condition is rare in the group, so false alerts outnumber true ones

When a condition is rare, even a small false-positive rate applied to a very large group yields more false alerts than true findings, so the positive predictive value collapses. The implication is a system one: the clinics that absorb the follow-up appointments are stakeholders in a decision taken by a consumer electronics firm.

After the US Supreme Court's Dobbs decision of June 2022 removed the constitutional right to abortion, many users deleted period-tracking apps, and one large app introduced an anonymous mode. The reaction illustrates the implication that

• data recorded for self-care can later serve as evidence against the user
• health apps are forbidden from storing reproductive data in the United States
• app stores remove health apps whenever the law that applies to them changes
• cycle predictions become inaccurate when data is stored anonymously

Answer: data recorded for self-care can later serve as evidence against the user

The data's meaning changed with the legal context: entries made for self-tracking could, under subpoena, indicate a pregnancy and its end, so the risk is downstream reuse, not the app's original purpose. No US rule bans such storage — that distractor mistakes the absence of protection for a prohibition.